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SubjectRe: [PATCH V6 2/7] soc: qcom: dcc:Add driver support for Data Capture and Compare unit(DCC)
On Tue 10 Aug 12:54 CDT 2021, Souradeep Chowdhury wrote:

> The DCC is a DMA Engine designed to capture and store data
> during system crash or software triggers.The DCC operates

Please include a space after '.'

> based on user inputs via the sysfs interface.The user gives
> addresses as inputs and these addresses are stored in the
> form of linkedlists.In case of a system crash or a manual

I think the user configures the DCC hardware with "a sequence of
operations to be performed as DCC is triggered".

Afaict the sequence is stored just as a sequence of operations in SRAM,
there's no linked list involved - except in your intermediate
implementation.

> software trigger by the user through the sysfs interface,
> the dcc captures and stores the values at these addresses.
> This patch contains the driver which has all the methods
> pertaining to the sysfs interface, auxiliary functions to
> support all the four fundamental operations of dcc namely
> read, write, first read then write and loop.The probe method

"first read then write" is called "read/modify/write"

> here instantiates all the resources necessary for dcc to
> operate mainly the dedicated dcc sram where it stores the
> values.The DCC driver can be used for debugging purposes
> without going for a reboot since it can perform manual
> triggers.
>
> Also added the documentation for sysfs entries
> and explained the functionalities of each sysfs file that
> has been created for dcc.
>
> The following is the justification of using sysfs interface
> over the other alternatives like ioctls
>
> i) As can be seen from the sysfs attribute descriptions,
> most of it does basic hardware manipulations like dcc_enable,
> dcc_disable, config reset etc. As a result sysfs is preferred
> over ioctl as we just need to enter a 0 or 1.
>

As I mentioned in our chat, using sysfs allows us to operate the
interface using the shell without additional tools.

But I don't think that it's easy to implement enable/disable/reset using
sysfs is a strong argument. The difficult part of this ABI is the
operations to manipulate the sequence of operations, so that's what you
need to have a solid plan for.

> ii) Existing similar debug hardwares are there for which drivers
> have been written using sysfs interface.One such example is the
> coresight-etm-trace driver.

Afaict the etm interface has operations to enable and disable, I don't
see anything that's similar to the interface for defining the sequence
of operations.

> A closer analog can also be the watchdog
> subsystems though it is ioctls based.
>

I don't think this adds value to the argument for using a sysfs based
interface.

> Signed-off-by: Souradeep Chowdhury <schowdhu@codeaurora.org>
> ---
> Documentation/ABI/testing/sysfs-driver-dcc | 114 ++
> drivers/soc/qcom/Kconfig | 8 +
> drivers/soc/qcom/Makefile | 1 +
> drivers/soc/qcom/dcc.c | 1549 ++++++++++++++++++++++++++++
> 4 files changed, 1672 insertions(+)
> create mode 100644 Documentation/ABI/testing/sysfs-driver-dcc
> create mode 100644 drivers/soc/qcom/dcc.c
>
> diff --git a/Documentation/ABI/testing/sysfs-driver-dcc b/Documentation/ABI/testing/sysfs-driver-dcc
> new file mode 100644
> index 0000000..05d24f0
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-driver-dcc
> @@ -0,0 +1,114 @@
> +What: /sys/bus/platform/devices/.../trigger
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This is the sysfs interface for manual software
> + triggers.The user can simply enter a 1 against
> + the sysfs file and enable a manual trigger.
> + Example:
> + echo 1 > /sys/bus/platform/devices/.../trigger
> +
> +What: /sys/bus/platform/devices/.../enable
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This sysfs interface is used for enabling the
> + the dcc hardware.Without this being set to 1,
> + the dcc hardware ceases to function.
> + Example:
> + echo 0 > /sys/bus/platform/devices/.../enable
> + (disable interface)
> + echo 1 > /sys/bus/platform/devices/.../enable
> + (enable interface)
> +
> +What: /sys/bus/platform/devices/.../config
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This is the most commonly used sysfs interface

No reason to mention that this is the most commonly used attribute, with
the right description that will be obvious.

> + file and this basically stores the addresses of
> + the registers which needs to be read in case of
> + a hardware crash or manual software triggers.

This doesn't "basically store the..." it "appends a set of registers to
include in the snapshot to the currently selected list".

The description should cover the format at well, in particular there's
nothing in "the addresses" that indicates that it takes 1, 2 or 3
parameters.

> + Example:
> + echo 0x80000010 10 > /sys/bus/platform/devices/../config
> + This specifies that 10 words starting from address
> + 0x80000010 is to be read.In case there are no words to be
> + specified we can simply enter the address.
> +
> +What: /sys/bus/platform/devices/.../config_write
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This file allows user to write a value to the register
> + address given as argument.The values are entered in the
> + form of <register_address> <value>.The reason for this
> + feature of dcc is that for accessing certain registers
> + it is necessary to set some bits of soe other register.
> + That is achievable by giving DCC this privelege.
> + Example:
> + echo 0x80000000 0xFF > /sys/bus/platform/devices/.../config_write
> +
> +What: /sys/bus/platform/devices/.../config_reset
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This file is used to reset the configuration of
> + a dcc driver to the default configuration.
> + Example:
> + echo 1 > /sys/bus/platform/devices/.../config_reset
> +
> +What: /sys/bus/platform/devices/.../loop
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This file is used to enter the loop count as dcc
> + driver gives the option to loop multiple times on
> + the same register and store the values for each
> + loop.This is done to capture the changing values
> + of a register with time which comes handy for
> + debugging purposes.
> + Example:
> + echo 10 > /sys/bus/platform/devices/10a2000.dcc/loop
> + (Setting the loop count to 10)
> + echo 0x80000010 10 > /sys/bus/platform/devices/.../config
> + (Read 10 words starting from address 0x80000010O)
> + echo 1 > /sys/bus/platform/devices/.../loop
> + (Terminate the loop by writing a count of 1 to the loop sysfs node)
> +
> +What: /sys/bus/platform/devices/.../rd_mod_wr
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This file is used to read the value of the register
> + and then write the value given as an argument to the
> + register address in config.

It's not clear from this description how to use this operation. E.g. is
it appended to the same list of operations? When will this operation
happen?

Looking at the implementation I believe that "config", "config_write",
"loop" and "rd_mod_wr" all appends operations to the same list.

I think it would be much better to configure this with a single file
that can either be written to '>' or appended to '>>' and you would feed
it a sequence of the operations to be performed.

That said, I'm afraid that might no longer be a sysfs attribute.

Something like:
# echo 'r 0x80000010 0x10' > config
# echo 'w 0x80000000 0xff' >> config
# echo 'rmw 0x80000000 0xf 0xa' >> config
# echo 'l 0x80000010 10' >> config

and:
# cat config
r 0x80000010 0x10
w 0x80000000 0xff
rmw 0x80000000 0xf 0xa
l 0x80000010 10

(Or read/write/modify/loop as keywords...)


reset could be done by just: echo '' > config

This would make it quite similar to several of the files in the tracing
framework.

> + The address argument should
> + be given of the form <mask> <value>.For debugging
> + purposes sometimes we need to first read from a register
> + and then set some values to the register.
> + Example:
> + echo 0x80000000 > /sys/bus/platform/devices/.../config
> + (Set the address in config file)
> + echo 0xF 0xA > /sys/bus/platform/devices/.../rd_mod_wr
> + (Provide the mask and the value to write)
> +
> +What: /sys/bus/platform/devices/.../ready
> +Date: March 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This file is used to check the status of the dcc
> + hardware if it's ready to take the inputs.

When will this read "false"?

> + Example:
> + cat /sys/bus/platform/devices/.../ready
> +
> +What: /sys/bus/platform/devices/.../curr_list
> +Date: February 2021
> +Contact: Souradeep Chowdhury <schowdhu@codeaurora.org>
> +Description:
> + This attribute is used to enter the linklist to be

I think it would be more appropriate to use the verb "select" here and
afaict it's a "list" as the "linked" part only relates to your
implementation).

But that said, I don't like this ABI. I think it would be cleaner if you
had specific attributes for each of the lists. That way it would be
clear that you have N lists and they can be configured and enabled
independently, and there's no possible race conditions.

> + used while appending addresses.The range of values
> + for this can be from 0 to 3.This feature is given in
> + order to use certain linkedlist for certain debugging
> + purposes.
> + Example:
> + echo 0 > /sys/bus/platform/devices/10a2000.dcc/curr_list
> +
> diff --git a/drivers/soc/qcom/Kconfig b/drivers/soc/qcom/Kconfig
> index 79b568f..5101912 100644
> --- a/drivers/soc/qcom/Kconfig
> +++ b/drivers/soc/qcom/Kconfig
> @@ -69,6 +69,14 @@ config QCOM_LLCC
> SDM845. This provides interfaces to clients that use the LLCC.
> Say yes here to enable LLCC slice driver.
>
> +config QCOM_DCC
> + tristate "Qualcomm Technologies, Inc. Data Capture and Compare(DCC) engine driver"
> + depends on ARCH_QCOM || COMPILE_TEST
> + help
> + This option enables driver for Data Capture and Compare engine. DCC
> + driver provides interface to configure DCC block and read back
> + captured data from DCC's internal SRAM.
> +
> config QCOM_KRYO_L2_ACCESSORS
> bool
> depends on ARCH_QCOM && ARM64 || COMPILE_TEST
> diff --git a/drivers/soc/qcom/Makefile b/drivers/soc/qcom/Makefile
> index ad675a6..0aaf82b 100644
> --- a/drivers/soc/qcom/Makefile
> +++ b/drivers/soc/qcom/Makefile
> @@ -4,6 +4,7 @@ obj-$(CONFIG_QCOM_AOSS_QMP) += qcom_aoss.o
> obj-$(CONFIG_QCOM_GENI_SE) += qcom-geni-se.o
> obj-$(CONFIG_QCOM_COMMAND_DB) += cmd-db.o
> obj-$(CONFIG_QCOM_CPR) += cpr.o
> +obj-$(CONFIG_QCOM_DCC) += dcc.o
> obj-$(CONFIG_QCOM_GSBI) += qcom_gsbi.o
> obj-$(CONFIG_QCOM_MDT_LOADER) += mdt_loader.o
> obj-$(CONFIG_QCOM_OCMEM) += ocmem.o
> diff --git a/drivers/soc/qcom/dcc.c b/drivers/soc/qcom/dcc.c
> new file mode 100644
> index 0000000..daf4388
> --- /dev/null
> +++ b/drivers/soc/qcom/dcc.c
> @@ -0,0 +1,1549 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2015-2021, The Linux Foundation. All rights reserved.
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/bitops.h>
> +#include <linux/cdev.h>
> +#include <linux/delay.h>
> +#include <linux/fs.h>
> +#include <linux/io.h>
> +#include <linux/iopoll.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +#include <linux/uaccess.h>
> +
> +#define TIMEOUT_US 5000
> +
> +#define dcc_writel(drvdata, val, off) \
> + writel((val), drvdata->base + dcc_offset_conv(drvdata, off))
> +#define dcc_readl(drvdata, off) \
> + readl(drvdata->base + dcc_offset_conv(drvdata, off))
> +
> +#define DCC_SRAM_NODE "dcc_sram"
> +
> +/* DCC registers */
> +#define DCC_HW_INFO 0x04
> +#define DCC_LL_NUM_INFO 0x10
> +#define DCC_STATUS 0x1C
> +#define DCC_LL_LOCK(m) (0x34 + 0x80 * m)
> +#define DCC_LL_CFG(m) (0x38 + 0x80 * m)
> +#define DCC_LL_BASE(m) (0x3c + 0x80 * m)
> +#define DCC_FD_BASE(m) (0x40 + 0x80 * m)
> +#define DCC_LL_TIMEOUT(m) (0x44 + 0x80 * m)
> +#define DCC_LL_INT_ENABLE(m) (0x4C + 0x80 * m)
> +#define DCC_LL_INT_STATUS(m) (0x50 + 0x80 * m)
> +#define DCC_LL_SW_TRIGGER(m) (0x60 + 0x80 * m)
> +#define DCC_LL_BUS_ACCESS_STATUS(m) (0x64 + 0x80 * m)
> +
> +#define DCC_MAP_LEVEL1 0x18
> +#define DCC_MAP_LEVEL2 0x34
> +#define DCC_MAP_LEVEL3 0x4C
> +
> +#define DCC_MAP_OFFSET1 0x10
> +#define DCC_MAP_OFFSET2 0x18
> +#define DCC_MAP_OFFSET3 0x1C
> +#define DCC_MAP_OFFSET4 0x8
> +
> +#define DCC_FIX_LOOP_OFFSET 16
> +#define DCC_VER_INFO_BIT 9
> +
> +#define DCC_READ 0
> +#define DCC_WRITE 1
> +#define DCC_LOOP 2
> +#define DCC_READ_WRITE 3
> +
> +#define MAX_DCC_OFFSET GENMASK(9, 2)
> +#define MAX_DCC_LEN GENMASK(6, 0)
> +#define MAX_LOOP_CNT GENMASK(7, 0)
> +
> +#define DCC_ADDR_DESCRIPTOR 0x00
> +#define DCC_ADDR_LIMIT 27
> +#define DCC_ADDR_OFF_RANGE 8
> +#define DCC_ADDR_RANGE GENMASK(31, 4)
> +#define DCC_LOOP_DESCRIPTOR BIT(30)
> +#define DCC_RD_MOD_WR_DESCRIPTOR BIT(31)
> +#define DCC_LINK_DESCRIPTOR GENMASK(31, 30)
> +
> +#define DCC_READ_IND 0x00
> +#define DCC_WRITE_IND (BIT(28))
> +
> +#define DCC_AHB_IND 0x00
> +#define DCC_APB_IND BIT(29)
> +
> +#define DCC_MAX_LINK_LIST 8
> +#define DCC_INVALID_LINK_LIST GENMASK(7, 0)
> +
> +#define DCC_VER_MASK1 GENMASK(6, 0)
> +#define DCC_VER_MASK2 GENMASK(5, 0)
> +
> +#define DCC_RD_MOD_WR_ADDR 0xC105E
> +
> +struct qcom_dcc_config {
> + int dcc_ram_offset;
> +};
> +
> +enum dcc_descriptor_type {
> + DCC_ADDR_TYPE,
> + DCC_LOOP_TYPE,
> + DCC_READ_WRITE_TYPE,
> + DCC_WRITE_TYPE
> +};
> +
> +enum dcc_mem_map_ver {
> + DCC_MEM_MAP_VER1 = 1,
> + DCC_MEM_MAP_VER2 = 2,
> + DCC_MEM_MAP_VER3 = 3
> +};
> +
> +struct dcc_config_entry {
> + u32 base;
> + u32 offset;
> + u32 len;
> + u32 index;
> + u32 loop_cnt;
> + u32 write_val;
> + u32 mask;
> + bool apb_bus;
> + enum dcc_descriptor_type desc_type;
> + struct list_head list;
> +};
> +
> +/**
> + * struct dcc_drvdata - configuration information related to a dcc device
> + * @base: Base Address of the dcc device
> + * @dev: The device attached to the driver data
> + * @mutex: Lock to protect access and manipulation of dcc_drvdata
> + * @ram_base: Base address for the SRAM dedicated for the dcc device
> + * @ram_offset: Offset to the SRAM dedicated for dcc device
> + * @mem_map_ver: Memory map version of DCC hardware
> + * @ram_cfg: Used for address limit calculation for dcc
> + * @ram_start: Starting address of DCC SRAM
> + * @enable: Flag to check if DCC linked list is enabled
> + * @interrupt_disable:Flag to enable/disable interrupts
> + * @sram_dev: Character device equivalent of dcc SRAM
> + * @sram_class: Class equivalent of the DCC SRAM device
> + * @cfg_head: Points to the head of the linked list of addresses
This isn't a list "of addresses" it's the list of operations that, when
written to sram, will be executed when the DCC trigger happens.

> + * @nr_config: Stores the number of addresses currently configured for a linkedlist
> + * @nr_link_list: Total number of linkedlists supported by the DCC configuration
> + * @curr_list: The index of the current linklist with which the driver is working
> + * @loopoff: Loop offset bits range for the addresses
> + */
> +struct dcc_drvdata {
> + void __iomem *base;
> + struct device *dev;
> + struct mutex mutex;
> + void __iomem *ram_base;
> + phys_addr_t ram_size;

ram_size sounds like a size_t

> + phys_addr_t ram_offset;

This can be size_t as well, or unsigned int.

> + enum dcc_mem_map_ver mem_map_ver;
> + phys_addr_t ram_cfg;
> + phys_addr_t ram_start;
> + bool *enable;
> + bool interrupt_disable;
> + struct cdev sram_dev;
> + struct class *sram_class;
> + struct list_head *cfg_head;
> + size_t *nr_config;
> + size_t nr_link_list;
> + u8 curr_list;
> + u8 loopoff;
> +};
> +
> +struct dcc_cfg_attr {
> + u32 addr;
> + u32 prev_addr;
> + u32 prev_off;
> + u32 link;
> + u32 sram_offset;
> +};
> +
> +struct dcc_cfg_loop_attr {
> + u32 loop;
> + bool loop_start;
> + u32 loop_cnt;
> + u32 loop_len;
> + u32 loop_off;
> +};
> +
> +static size_t dcc_offset_conv(struct dcc_drvdata *drvdata, size_t off)
> +{
> + if (drvdata->mem_map_ver == DCC_MEM_MAP_VER1) {
> + if ((off & DCC_VER_MASK1) >= DCC_MAP_LEVEL3)
> + return off - DCC_MAP_OFFSET3;
> + if ((off & DCC_VER_MASK1) >= DCC_MAP_LEVEL2)
> + return off - DCC_MAP_OFFSET2;
> + else if ((off & DCC_VER_MASK1) >= DCC_MAP_LEVEL1)
> + return off - DCC_MAP_OFFSET1;
> + } else if (drvdata->mem_map_ver == DCC_MEM_MAP_VER2) {
> + if ((off & DCC_VER_MASK1) >= DCC_MAP_LEVEL2)
> + return off - DCC_MAP_OFFSET4;
> + }
> +
> + return off;
> +}
> +
> +static int dcc_sram_writel(struct dcc_drvdata *drvdata,
> + u32 val, u32 off)
> +{
> + if (unlikely(off > (drvdata->ram_size - 4)))
> + return -EINVAL;

ENOSPC seems better

> +
> + writel(val, drvdata->ram_base + off);
> +
> + return 0;
> +}
> +
> +static bool dcc_ready(struct dcc_drvdata *drvdata)

This name gives a feeling that it might relate to the "ready" sysfs
attribute, but it's actually "dcc_sw_trigger_done()", so I think it
would be better to just inline the readl_poll_timeout() directly in
dcc_sw_trigger().

> +{
> + u32 val;
> +
> + return !readl_poll_timeout((drvdata->base + dcc_offset_conv(drvdata, DCC_STATUS)),
> + val, (FIELD_GET(GENMASK(1, 0), val) == 0), 1, TIMEOUT_US);

GENMASK(1,0) would be better represented by well named define.

> +
> +}
> +
> +static int dcc_read_status(struct dcc_drvdata *drvdata)

This function name gives an impression that you're just querying the
state, but it seems to be doing "read and clear".

> +{
> + int curr_list;
> + u32 bus_status;
> + u32 ll_cfg;
> + u32 tmp_ll_cfg;
> +
> + for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {

I find it confusing that you're using curr_list as iterator in these
local functions as well as denoting the currently selected list.

If you just made the local variable "i" it would be obvious that it's a
local iterator/index.

> + if (!drvdata->enable[curr_list])
> + continue;
> +
> + bus_status = dcc_readl(drvdata, DCC_LL_BUS_ACCESS_STATUS(curr_list));
> +
> + if (bus_status) {
> + dev_err(drvdata->dev,
> + "Read access error for list %d err: 0x%x.\n",
> + curr_list, bus_status);
> +
> + ll_cfg = dcc_readl(drvdata, DCC_LL_CFG(curr_list));
> + tmp_ll_cfg = ll_cfg & ~BIT(9);

Can we have a define for BIT(9) in this register?

> + dcc_writel(drvdata, tmp_ll_cfg, DCC_LL_CFG(curr_list));
> + dcc_writel(drvdata, 0x3,

Same for 0x3?

> + DCC_LL_BUS_ACCESS_STATUS(curr_list));
> + dcc_writel(drvdata, ll_cfg, DCC_LL_CFG(curr_list));
> + return -ENODATA;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static int dcc_sw_trigger(struct dcc_drvdata *drvdata)
> +{
> + int ret;
> + int curr_list;
> + u32 ll_cfg;
> + u32 tmp_ll_cfg;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
> + if (!drvdata->enable[curr_list])
> + continue;
> + ll_cfg = dcc_readl(drvdata, DCC_LL_CFG(curr_list));
> + tmp_ll_cfg = ll_cfg & ~BIT(9);
> + dcc_writel(drvdata, tmp_ll_cfg, DCC_LL_CFG(curr_list));
> + dcc_writel(drvdata, 1, DCC_LL_SW_TRIGGER(curr_list));
> + dcc_writel(drvdata, ll_cfg, DCC_LL_CFG(curr_list));
> + }
> +
> + if (!dcc_ready(drvdata)) {
> + dev_err(drvdata->dev,
> + "DCC is busy after receiving sw tigger.\n");
> + ret = -EBUSY;
> + goto err;
> + }
> +
> + ret = dcc_read_status(drvdata);
> +
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static void _dcc_ll_cfg_reset_link(struct dcc_cfg_attr *cfg)
> +{
> + cfg->addr = 0x00;
> + cfg->link = 0;
> + cfg->prev_off = 0;
> + cfg->prev_addr = cfg->addr;
> +}
> +
> +static int _dcc_ll_cfg_read_write(struct dcc_drvdata *drvdata,
> + struct dcc_config_entry *entry,
> + struct dcc_cfg_attr *cfg)
> +{
> + int ret;
> +
> + if (cfg->link) {
> + /*
> + * write new offset = 1 to continue
> + * processing the list
> + */
> +
> + ret = dcc_sram_writel(drvdata, cfg->link, cfg->sram_offset);

This api seems rather "raw" and every time you call it you need to check
the return value and increment sram_offset with 4.

I think it would be nicer if you passed &cfg->sram_offset and
incremented that inside the function. You could go further by not
providing a return value and just speculatively perform all the
dcc_sram_writel() operations and then finally check if it overflowed at
the end of __dcc_ll_cfg().

> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> + /* Reset link and prev_off */
> + _dcc_ll_cfg_reset_link(cfg);
> + }
> +
> + cfg->addr = DCC_RD_MOD_WR_DESCRIPTOR;
> + ret = dcc_sram_writel(drvdata, cfg->addr, cfg->sram_offset);
> + if (ret)
> + return ret;
> +
> + cfg->sram_offset += 4;
> + ret = dcc_sram_writel(drvdata, entry->mask, cfg->sram_offset);
> + if (ret)
> + return ret;
> +
> + cfg->sram_offset += 4;
> + ret = dcc_sram_writel(drvdata, entry->write_val, cfg->sram_offset);
> + if (ret)
> + return ret;
> +
> + cfg->sram_offset += 4;
> + cfg->addr = 0;
> + return ret;
> +}
> +
> +static int _dcc_ll_cfg_loop(struct dcc_drvdata *drvdata, struct dcc_config_entry *entry,
> + struct dcc_cfg_attr *cfg,
> + struct dcc_cfg_loop_attr *cfg_loop,
> + u32 *total_len)
> +{
> +
> + int ret;
> +
> + /* Check if we need to write link of prev entry */
> + if (cfg->link) {
> + ret = dcc_sram_writel(drvdata, cfg->link, cfg->sram_offset);
> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> + }
> +
> + if (cfg_loop->loop_start) {

So you simply add an even number of loop entries in your list and every
even one is supposed to jump to the previous odd one.

> + cfg_loop->loop = (cfg->sram_offset - cfg_loop->loop_off) / 4;
> + cfg_loop->loop |= (cfg_loop->loop_cnt << drvdata->loopoff) &
> + GENMASK(DCC_ADDR_LIMIT, drvdata->loopoff);
> + cfg_loop->loop |= DCC_LOOP_DESCRIPTOR;
> + *total_len += (*total_len - cfg_loop->loop_len) * cfg_loop->loop_cnt;
> +
> + ret = dcc_sram_writel(drvdata, cfg_loop->loop, cfg->sram_offset);
> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> +
> + cfg_loop->loop_start = false;
> + cfg_loop->loop_len = 0;
> + cfg_loop->loop_off = 0;
> + } else {
> + cfg_loop->loop_start = true;
> + cfg_loop->loop_cnt = entry->loop_cnt - 1;
> + cfg_loop->loop_len = *total_len;
> + cfg_loop->loop_off = cfg->sram_offset;
> + }
> +
> + /* Reset link and prev_off */
> + _dcc_ll_cfg_reset_link(cfg);
> +
> + return ret;
> +}
> +
> +static int _dcc_ll_cfg_write(struct dcc_drvdata *drvdata,
> + struct dcc_config_entry *entry,
> + struct dcc_cfg_attr *cfg,
> + u32 *total_len)
> +{
> + u32 off;
> + int ret;
> +
> + if (cfg->link) {
> + /*
> + * write new offset = 1 to continue
> + * processing the list
> + */
> + ret = dcc_sram_writel(drvdata, cfg->link, cfg->sram_offset);
> +
> + if (ret)
> + return ret;
> +
> + cfg->sram_offset += 4;
> + /* Reset link and prev_off */
> + cfg->addr = 0x00;
> + cfg->prev_off = 0;
> + cfg->prev_addr = cfg->addr;
> + }
> +
> + off = entry->offset/4;
> + /* write new offset-length pair to correct position */
> + cfg->link |= ((off & GENMASK(7, 0)) | BIT(15) | ((entry->len << 8) & GENMASK(14, 8)));
> + cfg->link |= DCC_LINK_DESCRIPTOR;
> +
> + /* Address type */
> + cfg->addr = (entry->base >> 4) & GENMASK(DCC_ADDR_LIMIT, 0);
> + if (entry->apb_bus)
> + cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_APB_IND;
> + else
> + cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_WRITE_IND | DCC_AHB_IND;
> + ret = dcc_sram_writel(drvdata, cfg->addr, cfg->sram_offset);
> +
> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> +
> + ret = dcc_sram_writel(drvdata, cfg->link, cfg->sram_offset);
> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> +
> + ret = dcc_sram_writel(drvdata, entry->write_val, cfg->sram_offset);
> +
> + if (ret)
> + return ret;
> +
> + cfg->sram_offset += 4;
> + cfg->addr = 0x00;
> + cfg->link = 0;
> + return ret;
> +}
> +
> +static int _dcc_ll_cfg_default(struct dcc_drvdata *drvdata,

Why is this called "default" and not "read"?

> + struct dcc_config_entry *entry,
> + struct dcc_cfg_attr *cfg,
> + u32 *pos, u32 *total_len)
> +{
> + int ret;
> + u32 off;
> + u32 temp_off;
> +
> + cfg->addr = (entry->base >> 4) & GENMASK(27, 0);
> +
> + if (entry->apb_bus)
> + cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_APB_IND;
> + else
> + cfg->addr |= DCC_ADDR_DESCRIPTOR | DCC_READ_IND | DCC_AHB_IND;
> +
> + off = entry->offset/4;
> +
> + *total_len += entry->len * 4;
> +
> + if (!cfg->prev_addr || cfg->prev_addr != cfg->addr || cfg->prev_off > off) {
> + /* Check if we need to write prev link entry */
> + if (cfg->link) {
> + ret = dcc_sram_writel(drvdata, cfg->link, cfg->sram_offset);
> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> + }
> + dev_dbg(drvdata->dev, "DCC: sram address 0x%x\n", cfg->sram_offset);
> +
> + /* Write address */
> + ret = dcc_sram_writel(drvdata, cfg->addr, cfg->sram_offset);
> +
> + if (ret)
> + return ret;
> +
> + cfg->sram_offset += 4;
> +
> + /* Reset link and prev_off */
> + cfg->link = 0;
> + cfg->prev_off = 0;
> + }
> +
> + if ((off - cfg->prev_off) > 0xFF || entry->len > MAX_DCC_LEN) {
> + dev_err(drvdata->dev, "DCC: Programming error Base: 0x%x, offset 0x%x\n",
> + entry->base, entry->offset);
> + ret = -EINVAL;
> + return ret;
> + }
> +
> + if (cfg->link) {
> + /*
> + * link already has one offset-length so new
> + * offset-length needs to be placed at
> + * bits [29:15]
> + */
> + *pos = 15;
> +
> + /* Clear bits [31:16] */
> + cfg->link &= GENMASK(14, 0);
> + } else {
> + /*
> + * link is empty, so new offset-length needs
> + * to be placed at bits [15:0]
> + */
> + *pos = 0;
> + cfg->link = 1 << 15;
> + }
> +
> + /* write new offset-length pair to correct position */
> + temp_off = (off-cfg->prev_off) & GENMASK(7, 0);
> + cfg->link |= temp_off |((entry->len << 8) & GENMASK(14, 8)) << *pos;
> +
> + cfg->link |= DCC_LINK_DESCRIPTOR;
> +
> + if (*pos) {
> + ret = dcc_sram_writel(drvdata, cfg->link, cfg->sram_offset);
> + if (ret)
> + return ret;
> + cfg->sram_offset += 4;
> + cfg->link = 0;
> + }
> +
> + cfg->prev_off = off + entry->len - 1;
> + cfg->prev_addr = cfg->addr;
> + return ret;
> +}
> +
> +static int __dcc_ll_cfg(struct dcc_drvdata *drvdata, int curr_list)

I guess this is an abbreviation of dcc_linked_list_config?

Why not something like dcc_emit_config() and then above might be
dcc_emit_read(), dcc_emit_write() etc?

> +{
> + int ret = 0;

Afaict this the first access to this is an assignment in all code paths,
so please skip the initialization.

> + u32 total_len, pos;
> + struct dcc_config_entry *entry;
> + struct dcc_cfg_attr cfg;
> + struct dcc_cfg_loop_attr cfg_loop;
> +
> + memset(&cfg, 0, sizeof(cfg));
> + memset(&cfg_loop, 0, sizeof(cfg_loop));
> + cfg.sram_offset = drvdata->ram_cfg * 4;
> + total_len = 0;
> +
> + list_for_each_entry(entry, &drvdata->cfg_head[curr_list], list) {
> + switch (entry->desc_type) {
> + case DCC_READ_WRITE_TYPE:
> + ret = _dcc_ll_cfg_read_write(drvdata, entry, &cfg);
> + if (ret)
> + goto overstep;
> + break;
> +
> + case DCC_LOOP_TYPE:
> + ret = _dcc_ll_cfg_loop(drvdata, entry, &cfg, &cfg_loop, &total_len);
> + if (ret)
> + goto overstep;
> + break;
> +
> + case DCC_WRITE_TYPE:
> + ret = _dcc_ll_cfg_write(drvdata, entry, &cfg, &total_len);
> + if (ret)
> + goto overstep;
> + break;
> +
> + default:
> + ret = _dcc_ll_cfg_default(drvdata, entry, &cfg, &pos, &total_len);
> + if (ret)
> + goto overstep;
> + break;
> + }
> + }
> +
> + if (cfg.link) {
> + ret = dcc_sram_writel(drvdata, cfg.link, cfg.sram_offset);
> + if (ret)
> + goto overstep;
> + cfg.sram_offset += 4;
> + }
> +
> + if (cfg_loop.loop_start) {
> + dev_err(drvdata->dev, "DCC: Programming error: Loop unterminated\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + /* Handling special case of list ending with a rd_mod_wr */
> + if (cfg.addr == DCC_RD_MOD_WR_DESCRIPTOR) {
> + cfg.addr = (DCC_RD_MOD_WR_ADDR) & GENMASK(27, 0);
> + cfg.addr |= DCC_ADDR_DESCRIPTOR;
> + ret = dcc_sram_writel(drvdata, cfg.addr, cfg.sram_offset);
> + if (ret)
> + goto overstep;
> + cfg.sram_offset += 4;
> + }
> +
> + /* Setting zero to indicate end of the list */
> + cfg.link = DCC_LINK_DESCRIPTOR;
> + ret = dcc_sram_writel(drvdata, cfg.link, cfg.sram_offset);
> + if (ret)
> + goto overstep;
> + cfg.sram_offset += 4;
> +
> + /* Update ram_cfg and check if the data will overstep */
> +
> + drvdata->ram_cfg = (cfg.sram_offset + total_len) / 4;
> +
> + if (cfg.sram_offset + total_len > drvdata->ram_size) {
> + cfg.sram_offset += total_len;
> + goto overstep;
> + }
> +
> + drvdata->ram_start = cfg.sram_offset/4;
> + return 0;
> +overstep:
> + ret = -EINVAL;
> + memset_io(drvdata->ram_base, 0, drvdata->ram_size);
> +
> +err:
> + return ret;
> +}
> +
> +static int dcc_valid_list(struct dcc_drvdata *drvdata, int curr_list)
> +{
> + u32 lock_reg;
> +
> + if (list_empty(&drvdata->cfg_head[curr_list]))
> + return -EINVAL;
> +
> + if (drvdata->enable[curr_list]) {
> + dev_err(drvdata->dev, "List %d is already enabled\n",
> + curr_list);
> + return -EINVAL;
> + }
> +
> + lock_reg = dcc_readl(drvdata, DCC_LL_LOCK(curr_list));

Under what circumstances would this differ from
drvdata->enable[curr_list}?
> + if (lock_reg & 0x1) {
> + dev_err(drvdata->dev, "List %d is already locked\n",
> + curr_list);
> + return -EINVAL;
> + }
> +
> + dev_err(drvdata->dev, "DCC list passed %d\n", curr_list);

This is noise, please drop it.

> + return 0;
> +}
> +
> +static bool is_dcc_enabled(struct dcc_drvdata *drvdata)
> +{
> + bool dcc_enable = false;
> + int list;
> +
> + for (list = 0; list < DCC_MAX_LINK_LIST; list++) {
> + if (drvdata->enable[list]) {

return true;

> + dcc_enable = true;
> + break;
> + }
> + }
> +

return false;

> + return dcc_enable;
> +}
> +
> +static int dcc_enable(struct dcc_drvdata *drvdata)
> +{
> + int ret = 0;
> + int list;
> + u32 ram_cfg_base;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + if (!is_dcc_enabled(drvdata)) {
> + memset_io(drvdata->ram_base,
> + 0xDE, drvdata->ram_size);

No need to wrap this line, and please use lowercase hex digits.

> + }
> +
> + for (list = 0; list < drvdata->nr_link_list; list++) {
> +

Please drop the empty line.

> + if (dcc_valid_list(drvdata, list))
> + continue;
> +
> + /* 1. Take ownership of the list */
> + dcc_writel(drvdata, BIT(0), DCC_LL_LOCK(list));

Can we have a define for BIT(0)? Is it really about ownership or just
that we "enable" it?

If ownership, who's the other contenders for the ownership?

> +
> + /* 2. Program linked-list in the SRAM */
> + ram_cfg_base = drvdata->ram_cfg;
> + ret = __dcc_ll_cfg(drvdata, list);
> + if (ret) {
> + dcc_writel(drvdata, 0, DCC_LL_LOCK(list));
> + goto err;
> + }
> +
> + /* 3. program DCC_RAM_CFG reg */
> + dcc_writel(drvdata, ram_cfg_base +
> + drvdata->ram_offset/4, DCC_LL_BASE(list));
> + dcc_writel(drvdata, drvdata->ram_start +
> + drvdata->ram_offset/4, DCC_FD_BASE(list));
> + dcc_writel(drvdata, 0xFFF, DCC_LL_TIMEOUT(list));
> +
> + /* 4. Clears interrupt status register */
> + dcc_writel(drvdata, 0, DCC_LL_INT_ENABLE(list));
> + dcc_writel(drvdata, (BIT(0) | BIT(1) | BIT(2)),
> + DCC_LL_INT_STATUS(list));
> +
> + drvdata->enable[list] = true;
> +
> + /* 5. Configure trigger */
> + dcc_writel(drvdata, BIT(9), DCC_LL_CFG(list));
> + }
> +
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static void dcc_disable(struct dcc_drvdata *drvdata)
> +{
> + int curr_list;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
> + if (!drvdata->enable[curr_list])
> + continue;
> + dcc_writel(drvdata, 0, DCC_LL_CFG(curr_list));
> + dcc_writel(drvdata, 0, DCC_LL_BASE(curr_list));
> + dcc_writel(drvdata, 0, DCC_FD_BASE(curr_list));
> + dcc_writel(drvdata, 0, DCC_LL_LOCK(curr_list));
> + drvdata->enable[curr_list] = false;
> + }
> + memset_io(drvdata->ram_base, 0, drvdata->ram_size);

Is there any reason why DCC is filled with 0xde during initialization
but 0 when disabled?

> + drvdata->ram_cfg = 0;
> + drvdata->ram_start = 0;
> + mutex_unlock(&drvdata->mutex);
> +}
> +
> +static ssize_t curr_list_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int ret;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + mutex_lock(&drvdata->mutex);
> + if (drvdata->curr_list == DCC_INVALID_LINK_LIST) {
> + dev_err(dev, "curr_list is not set.\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + ret = scnprintf(buf, PAGE_SIZE, "%d\n", drvdata->curr_list);
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static ssize_t curr_list_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> + unsigned long val;
> + u32 lock_reg;
> + bool dcc_enable = false;
> +
> + if (kstrtoul(buf, 16, &val))
> + return -EINVAL;
> +
> + if (val >= drvdata->nr_link_list)
> + return -EINVAL;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + dcc_enable = is_dcc_enabled(drvdata);
> + if (drvdata->curr_list != DCC_INVALID_LINK_LIST && dcc_enable) {
> + dev_err(drvdata->dev, "DCC is enabled, please disable it first.\n");
> + mutex_unlock(&drvdata->mutex);
> + return -EINVAL;
> + }
> +
> + lock_reg = dcc_readl(drvdata, DCC_LL_LOCK(val));
> + if (lock_reg & 0x1) {
> + dev_err(drvdata->dev, "DCC linked list is already configured\n");
> + mutex_unlock(&drvdata->mutex);
> + return -EINVAL;
> + }
> + drvdata->curr_list = val;
> + mutex_unlock(&drvdata->mutex);
> +
> + return size;
> +}
> +
> +static DEVICE_ATTR_RW(curr_list);
> +
> +
> +static ssize_t trigger_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int ret = 0;
> + unsigned long val;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + if (kstrtoul(buf, 16, &val))
> + return -EINVAL;
> + if (val != 1)
> + return -EINVAL;
> +
> + ret = dcc_sw_trigger(drvdata);
> + if (!ret)
> + ret = size;
> +
> + return ret;
> +}
> +static DEVICE_ATTR_WO(trigger);
> +
> +static ssize_t enable_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int ret;
> + bool dcc_enable = false;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + mutex_lock(&drvdata->mutex);
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(dev, "Select link list to program using curr_list\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + dcc_enable = is_dcc_enabled(drvdata);
> +
> + ret = scnprintf(buf, PAGE_SIZE, "%u\n",
> + (unsigned int)dcc_enable);
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static ssize_t enable_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int ret = 0;
> + unsigned long val;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + if (kstrtoul(buf, 16, &val))
> + return -EINVAL;
> +
> + if (val)
> + ret = dcc_enable(drvdata);
> + else
> + dcc_disable(drvdata);
> +
> + if (!ret)
> + ret = size;
> +
> + return ret;
> +
> +}
> +
> +static DEVICE_ATTR_RW(enable);
> +
> +static ssize_t config_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> + struct dcc_config_entry *entry;
> + char local_buf[64];
> + int len = 0, count = 0;
> +
> + mutex_lock(&drvdata->mutex);
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(dev, "Select link list to program using curr_list\n");
> + count = -EINVAL;
> + goto err;
> + }
> +
> + list_for_each_entry(entry,
> + &drvdata->cfg_head[drvdata->curr_list], list) {
> + switch (entry->desc_type) {
> + case DCC_READ_WRITE_TYPE:
> + len = snprintf(local_buf, 64, "Index: 0x%x, mask: 0x%x, val: 0x%x\n",
> + entry->index, entry->mask, entry->write_val);
> + break;
> + case DCC_LOOP_TYPE:
> + len = snprintf(local_buf, 64, "Index: 0x%x, Loop: %d\n",
> + entry->index, entry->loop_cnt);
> + break;
> + case DCC_WRITE_TYPE:
> + len = snprintf(local_buf, 64,
> + "Write Index: 0x%x, Base: 0x%x, Offset: 0x%x, len: 0x%x APB: %d\n",
> + entry->index, entry->base, entry->offset, entry->len,
> + entry->apb_bus);
> + break;
> + default:
> + len = snprintf(local_buf, 64,
> + "Read Index: 0x%x, Base: 0x%x, Offset: 0x%x, len: 0x%x APB: %d\n",
> + entry->index, entry->base, entry->offset,
> + entry->len, entry->apb_bus);
> + }
> +
> + if ((count + len) > PAGE_SIZE) {
> + dev_err(dev, "DCC: Couldn't write complete config\n");
> + break;
> + }
> + count += len;
> + }
> +
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return count;
> +}
> +
> +static int dcc_config_add(struct dcc_drvdata *drvdata, unsigned int addr,
> + unsigned int len, int apb_bus)
> +{
> + int ret;
> + struct dcc_config_entry *entry, *pentry;
> + unsigned int base, offset;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(drvdata->dev, "Select link list to program using curr_list\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + if (!len || len > (drvdata->ram_size / DCC_ADDR_OFF_RANGE)) {
> + dev_err(drvdata->dev, "DCC: Invalid length\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + base = addr & DCC_ADDR_RANGE;
> +
> + if (!list_empty(&drvdata->cfg_head[drvdata->curr_list])) {
> + pentry = list_last_entry(&drvdata->cfg_head[drvdata->curr_list],
> + struct dcc_config_entry, list);
> +
> + if (pentry->desc_type == DCC_ADDR_TYPE &&
> + addr >= (pentry->base + pentry->offset) &&
> + addr <= (pentry->base +
> + pentry->offset + MAX_DCC_OFFSET)) {
> +
> + /* Re-use base address from last entry */
> + base = pentry->base;
> +
> + if ((pentry->len * 4 + pentry->base + pentry->offset)
> + == addr) {
> + len += pentry->len;
> +
> + if (len > MAX_DCC_LEN)
> + pentry->len = MAX_DCC_LEN;
> + else
> + pentry->len = len;
> +
> + addr = pentry->base + pentry->offset +
> + pentry->len * 4;
> + len -= pentry->len;
> + }
> + }
> + }
> +
> + offset = addr - base;
> +
> + while (len) {
> + entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
> + if (!entry) {
> + ret = -ENOMEM;
> + goto err;
> + }
> +
> + entry->base = base;
> + entry->offset = offset;
> + entry->len = min_t(u32, len, MAX_DCC_LEN);
> + entry->index = drvdata->nr_config[drvdata->curr_list]++;

Every time you insert something in the list you calculate and store
"index", which I presume means that it will be the index'th entry in
sram. Why not just calculate this as you flush out the list to sram?

> + entry->desc_type = DCC_ADDR_TYPE;
> + entry->apb_bus = apb_bus;
> + INIT_LIST_HEAD(&entry->list);
> + list_add_tail(&entry->list,
> + &drvdata->cfg_head[drvdata->curr_list]);
> +
> + len -= entry->len;
> + offset += MAX_DCC_LEN * 4;
> + }
> +
> + mutex_unlock(&drvdata->mutex);
> + return 0;
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static ssize_t config_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int ret, len, apb_bus;
> + unsigned int base;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> + int nval;
> +
> + nval = sscanf(buf, "%x %i %d", &base, &len, &apb_bus);
> + if (nval <= 0 || nval > 3)
> + return -EINVAL;
> +
> + if (nval == 1) {
> + len = 1;
> + apb_bus = 0;
> + } else if (nval == 2) {
> + apb_bus = 0;
> + } else {
> + apb_bus = 1;
> + }
> +
> + ret = dcc_config_add(drvdata, base, len, apb_bus);
> + if (ret)
> + return ret;
> +
> + return size;
> +
> +}
> +
> +static DEVICE_ATTR_RW(config);
> +
> +static void dcc_config_reset(struct dcc_drvdata *drvdata)
> +{
> + struct dcc_config_entry *entry, *temp;
> + int curr_list;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + for (curr_list = 0; curr_list < drvdata->nr_link_list; curr_list++) {
> + list_for_each_entry_safe(entry, temp,
> + &drvdata->cfg_head[curr_list], list) {
> + list_del(&entry->list);
> + devm_kfree(drvdata->dev, entry);
> + drvdata->nr_config[curr_list]--;
> + }
> + }
> + drvdata->ram_start = 0;
> + drvdata->ram_cfg = 0;
> + mutex_unlock(&drvdata->mutex);
> +}
> +
> +
> +static ssize_t config_reset_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + unsigned long val;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + if (kstrtoul(buf, 16, &val))
> + return -EINVAL;
> +
> + if (val)
> + dcc_config_reset(drvdata);
> +
> + return size;
> +}
> +
> +static DEVICE_ATTR_WO(config_reset);
> +
> +static ssize_t ready_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + int ret;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + mutex_lock(&drvdata->mutex);
> +
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(dev, "Select link list to program using curr_list\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + if (!drvdata->enable[drvdata->curr_list]) {
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + ret = scnprintf(buf, PAGE_SIZE, "%u\n",
> + (unsigned int)FIELD_GET(BIT(1), dcc_readl(drvdata, DCC_STATUS)));
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static DEVICE_ATTR_RO(ready);
> +
> +static ssize_t interrupt_disable_show(struct device *dev,
> + struct device_attribute *attr,
> + char *buf)
> +{
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + return scnprintf(buf, PAGE_SIZE, "%u\n",
> + (unsigned int)drvdata->interrupt_disable);
> +}
> +
> +static ssize_t interrupt_disable_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + unsigned long val;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + if (kstrtoul(buf, 16, &val))
> + return -EINVAL;
> +
> + mutex_lock(&drvdata->mutex);
> + drvdata->interrupt_disable = (val ? 1:0);

This doesn't seem like it actually does something, and it's not
documented in the sysfs interface.

> + mutex_unlock(&drvdata->mutex);
> + return size;
> +}
> +
> +static DEVICE_ATTR_RW(interrupt_disable);
> +
> +static int dcc_add_loop(struct dcc_drvdata *drvdata, unsigned long loop_cnt)
> +{
> + struct dcc_config_entry *entry;
> +
> + entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
> + if (!entry)
> + return -ENOMEM;
> +
> + entry->loop_cnt = min_t(u32, loop_cnt, MAX_LOOP_CNT);
> + entry->index = drvdata->nr_config[drvdata->curr_list]++;
> + entry->desc_type = DCC_LOOP_TYPE;
> + INIT_LIST_HEAD(&entry->list);
> + list_add_tail(&entry->list, &drvdata->cfg_head[drvdata->curr_list]);
> +
> + return 0;
> +}
> +
> +static ssize_t loop_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int ret;
> + unsigned long loop_cnt;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + mutex_lock(&drvdata->mutex);
> +
> + if (kstrtoul(buf, 16, &loop_cnt)) {
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(dev, "Select link list to program using curr_list\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + ret = dcc_add_loop(drvdata, loop_cnt);
> + if (ret)
> + goto err;
> +
> + mutex_unlock(&drvdata->mutex);
> + return size;
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static DEVICE_ATTR_WO(loop);
> +
> +static int dcc_rd_mod_wr_add(struct dcc_drvdata *drvdata, unsigned int mask,
> + unsigned int val)
> +{
> + int ret = 0;
> + struct dcc_config_entry *entry;
> +
> + mutex_lock(&drvdata->mutex);
> +
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(drvdata->dev, "Select link list to program using curr_list\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + if (list_empty(&drvdata->cfg_head[drvdata->curr_list])) {
> + dev_err(drvdata->dev, "DCC: No read address programmed\n");
> + ret = -EPERM;
> + goto err;
> + }
> +
> + entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
> + if (!entry) {
> + ret = -ENOMEM;
> + goto err;
> + }
> +
> + entry->desc_type = DCC_READ_WRITE_TYPE;
> + entry->mask = mask;
> + entry->write_val = val;
> + entry->index = drvdata->nr_config[drvdata->curr_list]++;
> + INIT_LIST_HEAD(&entry->list);
> + list_add_tail(&entry->list, &drvdata->cfg_head[drvdata->curr_list]);
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;
> +}
> +
> +static ssize_t rd_mod_wr_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int ret;
> + int nval;
> + unsigned int mask, val;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + nval = sscanf(buf, "%x %x", &mask, &val);
> +
> + if (nval <= 1 || nval > 2)
> + return -EINVAL;
> +
> + ret = dcc_rd_mod_wr_add(drvdata, mask, val);
> + if (ret)
> + return ret;
> +
> + return size;
> +
> +}
> +
> +static DEVICE_ATTR_WO(rd_mod_wr);
> +
> +static int dcc_add_write(struct dcc_drvdata *drvdata, unsigned int addr,
> + unsigned int write_val, int apb_bus)
> +{
> + struct dcc_config_entry *entry;
> +
> + entry = devm_kzalloc(drvdata->dev, sizeof(*entry), GFP_KERNEL);
> + if (!entry)
> + return -ENOMEM;
> +
> + entry->desc_type = DCC_WRITE_TYPE;
> + entry->base = addr & GENMASK(31, 4);
> + entry->offset = addr - entry->base;
> + entry->write_val = write_val;
> + entry->index = drvdata->nr_config[drvdata->curr_list]++;
> + entry->len = 1;
> + entry->apb_bus = apb_bus;
> + INIT_LIST_HEAD(&entry->list);
> + list_add_tail(&entry->list, &drvdata->cfg_head[drvdata->curr_list]);
> +
> + return 0;
> +}
> +
> +static ssize_t config_write_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int ret;
> + int nval;
> + unsigned int addr, write_val;
> + int apb_bus = 0;
> + struct dcc_drvdata *drvdata = dev_get_drvdata(dev);
> +
> + mutex_lock(&drvdata->mutex);
> +
> + nval = sscanf(buf, "%x %x %d", &addr, &write_val, &apb_bus);
> +
> + if (nval <= 1 || nval > 3) {
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + if (drvdata->curr_list >= drvdata->nr_link_list) {
> + dev_err(dev, "Select link list to program using curr_list\n");
> + ret = -EINVAL;
> + goto err;
> + }
> +
> + if (nval == 3 && apb_bus != 0)
> + apb_bus = 1;
> +
> + ret = dcc_add_write(drvdata, addr, write_val, apb_bus);
> + if (ret)
> + goto err;
> +
> + mutex_unlock(&drvdata->mutex);
> + return size;
> +err:
> + mutex_unlock(&drvdata->mutex);
> + return ret;

The two tails are very similar, you should be able to combine the two.

> +}
> +
> +static DEVICE_ATTR_WO(config_write);
> +
> +static const struct device_attribute *dcc_attrs[] = {
> + &dev_attr_trigger,
> + &dev_attr_enable,
> + &dev_attr_config,
> + &dev_attr_config_reset,
> + &dev_attr_ready,
> + &dev_attr_interrupt_disable,
> + &dev_attr_loop,
> + &dev_attr_rd_mod_wr,
> + &dev_attr_curr_list,
> + &dev_attr_config_write,
> + NULL,
> +};
> +
> +static int dcc_create_files(struct device *dev,
> + const struct device_attribute **attrs)
> +{
> + int ret = 0, i;
> +
> + for (i = 0; attrs[i] != NULL; i++) {
> + ret = device_create_file(dev, attrs[i]);
> + if (ret) {
> + dev_err(dev, "DCC: Couldn't create sysfs attribute: %s\n",
> + attrs[i]->attr.name);
> + break;
> + }
> + }
> + return ret;
> +}
> +
> +static int dcc_sram_open(struct inode *inode, struct file *file)
> +{
> + struct dcc_drvdata *drvdata = container_of(inode->i_cdev,
> + struct dcc_drvdata,
> + sram_dev);
> + file->private_data = drvdata;
> +
> + return 0;
> +}
> +
> +static ssize_t dcc_sram_read(struct file *file, char __user *data,
> + size_t len, loff_t *ppos)
> +{
> + unsigned char *buf;
> + struct dcc_drvdata *drvdata = file->private_data;
> +
> + /* EOF check */
> + if (drvdata->ram_size <= *ppos)
> + return 0;
> +
> + if ((*ppos + len) > drvdata->ram_size)
> + len = (drvdata->ram_size - *ppos);
> +
> + buf = kzalloc(len, GFP_KERNEL);
> + if (!buf)
> + return -ENOMEM;
> +
> + memcpy_fromio(buf, drvdata->ram_base + *ppos, len);
> +
> + if (copy_to_user(data, buf, len)) {
> + dev_err(drvdata->dev, "DCC: Couldn't copy all data to user\n");
> + kfree(buf);
> + return -EFAULT;
> + }
> +
> + *ppos += len;
> +
> + kfree(buf);
> +
> + return len;
> +}
> +
> +static const struct file_operations dcc_sram_fops = {
> + .owner = THIS_MODULE,
> + .open = dcc_sram_open,
> + .read = dcc_sram_read,
> + .llseek = no_llseek,
> +};
> +
> +static int dcc_sram_dev_register(struct dcc_drvdata *drvdata)
> +{
> + int ret;
> + struct device *device;
> + dev_t dev;
> +
> + ret = alloc_chrdev_region(&dev, 0, 1, DCC_SRAM_NODE);
> + if (ret)
> + goto err_alloc;
> +
> + cdev_init(&drvdata->sram_dev, &dcc_sram_fops);
> +
> + drvdata->sram_dev.owner = THIS_MODULE;
> + ret = cdev_add(&drvdata->sram_dev, dev, 1);
> + if (ret)
> + goto err_cdev_add;
> +
> + drvdata->sram_class = class_create(THIS_MODULE, DCC_SRAM_NODE);
> + if (IS_ERR(drvdata->sram_class)) {
> + ret = PTR_ERR(drvdata->sram_class);
> + goto err_class_create;
> + }
> +
> + device = device_create(drvdata->sram_class, NULL,
> + drvdata->sram_dev.dev, drvdata,
> + DCC_SRAM_NODE);

Use misc_register() instead of rolling your own chrdev_region, cdev and
associated device.

> + if (IS_ERR(device)) {
> + ret = PTR_ERR(device);
> + goto err_dev_create;
> + }
> +
> + return 0;
> +err_dev_create:
> + class_destroy(drvdata->sram_class);
> +err_class_create:
> + cdev_del(&drvdata->sram_dev);
> +err_cdev_add:
> + unregister_chrdev_region(drvdata->sram_dev.dev, 1);
> +err_alloc:
> + return ret;
> +}
> +
> +static void dcc_sram_dev_deregister(struct dcc_drvdata *drvdata)
> +{
> + device_destroy(drvdata->sram_class, drvdata->sram_dev.dev);
> + class_destroy(drvdata->sram_class);
> + cdev_del(&drvdata->sram_dev);
> + unregister_chrdev_region(drvdata->sram_dev.dev, 1);
> +}
> +
> +static int dcc_sram_dev_init(struct dcc_drvdata *drvdata)
> +{
> + int ret = 0;
> +
> + ret = dcc_sram_dev_register(drvdata);

Why don't you simply call dcc_sram_dev_register() from probe?

> + if (ret)
> + dev_err(drvdata->dev, "DCC: sram node not registered.\n");
> +
> + return ret;
> +}
> +
> +static void dcc_sram_dev_exit(struct dcc_drvdata *drvdata)
> +{
> + dcc_sram_dev_deregister(drvdata);
> +}
> +
> +static int dcc_probe(struct platform_device *pdev)
> +{
> + u32 val;
> + int ret = 0, i, enable_size, nr_config_size, cfg_head_size;
> + struct device *dev = &pdev->dev;
> + struct dcc_drvdata *dcc;
> + struct resource *res;
> + const struct qcom_dcc_config *cfg;
> +
> + dcc = devm_kzalloc(dev, sizeof(*dcc), GFP_KERNEL);
> + if (!dcc)
> + return -ENOMEM;
> +
> + dcc->dev = &pdev->dev;
> + platform_set_drvdata(pdev, dcc);
> +
> + dcc->base = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(dcc->base))
> + return PTR_ERR(dcc->base);
> +
> + dcc->ram_base = devm_platform_get_and_ioremap_resource(pdev, 1, &res);
> + if (IS_ERR(dcc->ram_base))
> + return PTR_ERR(dcc->ram_base);
> +
> + dcc->ram_size = resource_size(res);
> +
> + dcc->ram_base = devm_ioremap(dev, res->start, resource_size(res));
> + if (!dcc->ram_base)
> + return -ENOMEM;
> +
> + cfg = of_device_get_match_data(&pdev->dev);
> + dcc->ram_offset = cfg->dcc_ram_offset;

ram_offset is always divided by 4 when read, so how about treating it as
"number of elements offset", rather than number of bytes?

> +
> + val = dcc_readl(dcc, DCC_HW_INFO);
> +
> + if (FIELD_GET(BIT(DCC_VER_INFO_BIT), val)) {
> + dcc->mem_map_ver = DCC_MEM_MAP_VER3;
> + dcc->nr_link_list = dcc_readl(dcc, DCC_LL_NUM_INFO);
> + if (dcc->nr_link_list == 0)
> + return -EINVAL;
> + } else if ((val & DCC_VER_MASK2) == DCC_VER_MASK2) {
> + dcc->mem_map_ver = DCC_MEM_MAP_VER2;
> + dcc->nr_link_list = dcc_readl(dcc, DCC_LL_NUM_INFO);
> + if (dcc->nr_link_list == 0)
> + return -EINVAL;
> + } else {
> + dcc->mem_map_ver = DCC_MEM_MAP_VER1;
> + dcc->nr_link_list = DCC_MAX_LINK_LIST;
> + }
> +
> + if ((val & BIT(6)) == BIT(6))

#define BIT(6) please

> + dcc->loopoff = DCC_FIX_LOOP_OFFSET;
> + else
> + dcc->loopoff = get_bitmask_order((dcc->ram_size +
> + dcc->ram_offset) / 4 - 1);
> +
> + mutex_init(&dcc->mutex);
> + /* Allocate space for all entries at once */
> + enable_size = dcc->nr_link_list * sizeof(bool);
> + nr_config_size = dcc->nr_link_list * sizeof(size_t);
> + cfg_head_size = dcc->nr_link_list * sizeof(struct list_head);
> +
> + dcc->enable = devm_kzalloc(dev, enable_size + nr_config_size + cfg_head_size, GFP_KERNEL);
> + if (!dcc->enable)
> + return -ENOMEM;
> +
> + dcc->nr_config = (size_t *)(dcc->enable + dcc->nr_link_list);
> + dcc->cfg_head = (struct list_head *)(dcc->nr_config + dcc->nr_link_list);

I find this overly complicated if it's true, as you wrote above, that
nr_link_list will be <= 4. Just make enable a bitmap, and nr_config and
statically sized arrays of length 4.

> +
> + for (i = 0; i < dcc->nr_link_list; i++)
> + INIT_LIST_HEAD(&dcc->cfg_head[i]);
> +
> + dcc->curr_list = DCC_INVALID_LINK_LIST;

Why don't you set this to 0, that way it's impossible for dcc->curr_list
to be an invalid number so you can remove all the checks of it being
invalid throughout the driver.

> + ret = dcc_sram_dev_init(dcc);
> + if (ret)
> + return ret;
> +
> + return dcc_create_files(dev, dcc_attrs);

If this fails you will leak the resources create in dcc_sram_dev_init()

> +}
> +
> +static int dcc_remove(struct platform_device *pdev)
> +{
> + struct dcc_drvdata *drvdata = platform_get_drvdata(pdev);

drvdata is named "dcc" in probe, that seems like a nicer name.

> +
> + dcc_sram_dev_exit(drvdata);
> +
> + dcc_config_reset(drvdata);
> +
> + return 0;
> +}
> +
> +static const struct qcom_dcc_config sm8150_cfg = {
> + .dcc_ram_offset = 0x5000,

Please just inline these into dcc_match_table[]

Regards,
Bjorn

> +};
> +
> +static const struct qcom_dcc_config sc7280_cfg = {
> + .dcc_ram_offset = 0x12000,
> +};
> +
> +static const struct qcom_dcc_config sc7180_cfg = {
> + .dcc_ram_offset = 0x6000,
> +};
> +
> +static const struct qcom_dcc_config sdm845_cfg = {
> + .dcc_ram_offset = 0x6000,
> +};
> +
> +static const struct of_device_id dcc_match_table[] = {
> + { .compatible = "qcom,sm8150-dcc", .data = &sm8150_cfg },
> + { .compatible = "qcom,sc7280-dcc", .data = &sc7280_cfg },
> + { .compatible = "qcom,sc7180-dcc", .data = &sc7180_cfg },
> + { .compatible = "qcom,sdm845-dcc", .data = &sdm845_cfg },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, dcc_match_table);
> +
> +static struct platform_driver dcc_driver = {
> + .probe = dcc_probe,
> + .remove = dcc_remove,
> + .driver = {
> + .name = "qcom-dcc",
> + .of_match_table = dcc_match_table,
> + },
> +};
> +
> +module_platform_driver(dcc_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_DESCRIPTION("Qualcomm Technologies Inc. DCC driver");
> +
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>

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