Messages in this thread | | | Subject | Re: [PATCH v4] drivers/coresight: Add Ultrasoc System Memory Buffer driver | From | "liuqi (BA)" <> | Date | Fri, 25 Mar 2022 16:25:39 +0800 |
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On 2022/3/24 20:37, Suzuki Kuruppassery Poulose wrote: > On 14/03/2022 10:04, liuqi (BA) wrote: >> >> >> On 2022/3/10 6:49, Suzuki K Poulose wrote: >>> Hi >>> >>> On 28/01/2022 06:17, Qi Liu wrote: >>>> This patch adds driver for Ultrasoc SMB(System Memory Buffer) >>>> device. SMB provides a way to buffer messages from ETM, and >>>> store these CPU instructions in system memory. >>>> >>>> SMB is developed by Ultrasoc technology, which is acquired by >>>> Siemens, and we still use "Ultrasoc" to name driver. >>>> >>>> Signed-off-by: Qi Liu <liuqi115@huawei.com> >>>> Tested-by: JunHao He <hejunhao2@hisilicon.com> >>> >>> Please find my comments below. In general : >>> >>> 1) Please run checkpatch and fix the warnings >>> 2) Add documentation for : >>> - A brief description of the device and the firmware bindings >>> (see comments below ) >>> - Sysfs attributes >>> 3) Other minor comments on the code >>> >> Hi Suzuki, >> >> thanks a lot for your review! and some replies inline. >>>> --- >> [...] >>>> --- a/drivers/hwtracing/coresight/Kconfig >>>> +++ b/drivers/hwtracing/coresight/Kconfig >>>> @@ -201,4 +201,14 @@ config CORESIGHT_TRBE >>>> To compile this driver as a module, choose M here: the >>>> module will be >>>> called coresight-trbe. >>>> +config ULTRASOC_SMB >>>> + tristate "Ultrasoc system memory buffer drivers" >>>> + depends on ARM64 && CORESIGHT_LINKS_AND_SINKS >>> >>> Given that this driver absolutely only works with ACPI, please could >>> you add that dependency here ? >> >> yes, I'll add this, thanks. >>> >>>> + help >>>> + This driver provides support for the Ultrasoc system memory >>>> buffer (SMB). >>>> + SMB is responsible for receiving the trace data from >>>> Coresight ETM devices >>>> + and storing them to a system buffer. >>>> + >>>> + To compile this driver as a module, choose M here: the module >>>> will be >>>> + called ultrasoc-smb. >>>> endif >>>> diff --git a/drivers/hwtracing/coresight/Makefile >>>> b/drivers/hwtracing/coresight/Makefile >>>> index b6c4a48140ec..344dba8d6ff8 100644 >>>> --- a/drivers/hwtracing/coresight/Makefile >>>> +++ b/drivers/hwtracing/coresight/Makefile >>>> @@ -27,3 +27,4 @@ obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o >>>> obj-$(CONFIG_CORESIGHT_TRBE) += coresight-trbe.o >>>> coresight-cti-y := coresight-cti-core.o coresight-cti-platform.o \ >>>> coresight-cti-sysfs.o >>>> +obj-$(CONFIG_ULTRASOC_SMB) += ultrasoc-smb.o >>>> diff --git a/drivers/hwtracing/coresight/ultrasoc-smb.c >>>> b/drivers/hwtracing/coresight/ultrasoc-smb.c >>>> new file mode 100644 >>>> index 000000000000..a18d061aab61 >>>> --- /dev/null >>>> +++ b/drivers/hwtracing/coresight/ultrasoc-smb.c >>>> @@ -0,0 +1,602 @@ >>>> +// SPDX-License-Identifier: MIT/GPL >>>> +/* >>>> + * Siemens System Memory Buffer driver. >>>> + * Copyright(c) 2022, HiSilicon Limited. >>>> + */ >>>> + >>>> +#include <linux/acpi.h> >>>> +#include <linux/circ_buf.h> >>>> +#include <linux/err.h> >>>> +#include <linux/module.h> >>>> +#include <linux/mod_devicetable.h> >>>> +#include <linux/platform_device.h> >>>> + >>>> +#include "ultrasoc-smb.h" >>>> + >>>> +DEFINE_CORESIGHT_DEVLIST(sink_devs, "smb"); >>> >>> minor nit: This name could be confused with SMB (samba) under linux >>> especially when it appears under /dev/smbN as a misc device. >>> >> got it, I'll rename this device. How about /dev/ultra_smbN? >>>> + >>>> +static bool smb_buffer_is_empty(struct smb_drv_data *drvdata) >>>> +{ >>>> + u32 buf_status = readl(drvdata->base + SMB_LB_INT_STS); >>>> + >>>> + return buf_status & BIT(0) ? false : true; >>>> +} >>>> + >> >> [...] >> >>>> + >>>> +static ssize_t smb_read(struct file *file, char __user *data, >>>> size_t len, loff_t *ppos) >>>> +{ >>>> + struct smb_drv_data *drvdata = container_of(file->private_data, >>>> + struct smb_drv_data, miscdev); >>>> + struct smb_data_buffer *sdb = &drvdata->sdb; >>>> + struct device *dev = &drvdata->csdev->dev; >>>> + unsigned long flags; >>>> + int to_copy = 0; >>>> + >>>> + spin_lock_irqsave(&drvdata->spinlock, flags); >>>> + >>>> + if (!sdb->data_size) { >>>> + smb_update_data_size(drvdata); >>>> + if (!sdb->data_size) >>>> + goto out; >>>> + } >>>> + >>>> + if (atomic_read(drvdata->csdev->refcnt)) { >>>> + to_copy = -EBUSY; >>>> + goto out; >>>> + } >>>> + >>> >>> Shouldn't this be performed *before* updating the data_size above ? >>> Looking at the smb_update_data_size() it "purges" the data. Is that >>> acceptable ? >> >> ah, yes, we should get this before updating the data_size. I'll fix >> this, thanks. >>> >>>> + to_copy = min(sdb->data_size, len); >>>> + >>>> + /* Copy parts of trace data when the read pointer will wrap >>>> around SMB buffer. */ >>>> + if (sdb->rd_offset + to_copy > sdb->buf_size) >> >> [...] >>>> +static struct attribute *smb_sink_attrs[] = { >>>> + &dev_attr_read_pos.attr, >>>> + &dev_attr_write_pos.attr, >>>> + &dev_attr_buf_status.attr, >>>> + &dev_attr_buf_size.attr, >>>> + NULL, >>>> +}; >>> >>> Please could you also update the sysfs ABI files with a brief >>> description of the above attributes ? >>> >>> e.g., Documentation/ABI/testing/sysfs-bus-coresight-devices-tmc >>> >> yes, sure. I'll do this. >> >>>> + >>>> +static const struct attribute_group smb_sink_group = { >>>> + .attrs = smb_sink_attrs, >>>> + .name = "status", >>>> +}; >>>> + >> [...] >>>> + >>>> +static int smb_enable_perf(struct smb_drv_data *drvdata, void *data) >>>> +{ >>>> + struct device *dev = &drvdata->csdev->dev; >>>> + struct perf_output_handle *handle = data; >>>> + pid_t pid; >>>> + >>>> + if (drvdata->mode == CS_MODE_SYSFS) { >>>> + dev_err(dev, "Device is already in used by sysfs\n"); >>> >>> Please could you convert this to dev_dbg() ? An -EBUSY should >>> be sufficient to indicate that the resource is busy. >>> >> got it, thanks, will fix this. >> >>>> + return -EBUSY; >>>> + } >>>> + >>>> + /* Get a handle on the pid of the target process*/ >>>> + pid = task_pid_nr(handle->event->owner); >>>> + if (drvdata->pid != -1 && drvdata->pid != pid) { >>>> + dev_err(dev, "Device is already in used by other session\n"); >>> >>> Same here. >>> >> ok. >>>> + return -EBUSY; >>>> + } >>>> + /* The sink is already enabled by this session. */ >>>> + if (drvdata->pid == pid) >>>> + return 0; >>> >>> If the sink is shared by multiple events of the same group, don't >>> we need a refcount to make sure we don't disable the buffer when >>> an event goes away ? >>> >> >> we increase this refcount in smb_enable(), if smb_enable_sysfs() or >> smb_enable_perf() is enabled successfully, we increase the refcount. >> >> So, when the sink is shared by multiple events of the same group, >> refcount will be increased too. thanks. > > I don't think this the case, at least by looking at the code. You need > to increment the refcount when you find that *this* session is going > to share the sink. > >>>> + >>>> + if (smb_set_perf_buffer(handle)) >>>> + return -EINVAL; >>>> + >>>> + smb_enable_hw(drvdata); >>>> + drvdata->pid = pid; >>>> + drvdata->mode = CS_MODE_PERF; >>>> + >>>> + return 0; >>>> +} >>>> + >>>> +static int smb_enable(struct coresight_device *csdev, u32 mode, >>>> void *data) >>>> +{ >>>> + struct smb_drv_data *drvdata = dev_get_drvdata(csdev->dev.parent); >>>> + unsigned long flags; >>>> + int ret = -EINVAL; >>>> + >>>> + /* Do nothing if trace data is reading by other interface now. */ >>>> + if (local_read(&drvdata->reading)) >>>> + return -EBUSY; >>>> + >>>> + spin_lock_irqsave(&drvdata->spinlock, flags); >>>> + >>>> + if (mode == CS_MODE_SYSFS) >>>> + ret = smb_enable_sysfs(drvdata); >>>> + >>>> + if (mode == CS_MODE_PERF) >>>> + ret = smb_enable_perf(drvdata, data); >>>> + >>>> + spin_unlock_irqrestore(&drvdata->spinlock, flags); >>>> + >>>> + if (ret) >>>> + return ret; >>>> + >>>> + atomic_inc(csdev->refcnt); > > Shouldn't this be done within the spinlock ? Othewise, we could have: > > > CPU0: smb_enable() { > CPU0: spin_lock() > CPU0: ... > CPU0: spin_unlock()... > CPU0: atomic_inc(refcnt) == 1; > CPU0: } > ... > > CPU0: smb_disable() { # Note CPU0 started to disable the session > > CPU1: smb_enable() { > CPU1: spin_lock() > CPU1: ... > CPU1: spin_unlock()... > > CPU0: spin_lock(); > > # Before the CPU1 increments the counter, CPU0 could see the recnt == 1 > # and go ahead to disable the HW. Where this must have been 2. > > > CPU0: if (!atomic_dec_return()) == 0 > CPU0: disable_hw(); > CPU1: atomic_inc(refcnt) == 1; > CPU0: spin_unlock() > CPU1: } >
Hi Suzuki,
got it, I'll increment the refcount in perf/sysfs session next version.
Thanks, Qi > > Suzuki > .
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