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    SubjectRe: [PATCH v1] regmap: add generic indirect regmap support
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    On 6/6/22 18:37, Tianfei Zhang wrote:
    > From: Matthew Gerlach <matthew.gerlach@linux.intel.com>
    >
    > This patch adds support for regmap APIs that are intended to be used by
    > the drivers of some devices which support generic indirect register access,
    > for example PMCI (Platform Management Control Interface) device, HSSI
    > (High Speed Serial Interface) device in FPGA.
    >
    > Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
    > Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
    > ---
    > drivers/base/regmap/Kconfig | 3 +
    > drivers/base/regmap/Makefile | 1 +
    > .../base/regmap/regmap-indirect-register.c | 133 ++++++++++++++++++
    > include/linux/regmap.h | 12 ++
    > 4 files changed, 149 insertions(+)
    > create mode 100644 drivers/base/regmap/regmap-indirect-register.c
    >
    > diff --git a/drivers/base/regmap/Kconfig b/drivers/base/regmap/Kconfig
    > index 159bac6c5046..4ea590604f8d 100644
    > --- a/drivers/base/regmap/Kconfig
    > +++ b/drivers/base/regmap/Kconfig
    > @@ -65,3 +65,6 @@ config REGMAP_I3C
    > config REGMAP_SPI_AVMM
    > tristate
    > depends on SPI
    > +
    > +config REGMAP_INDIRECT_REGISTER
    > + tristate
    > diff --git a/drivers/base/regmap/Makefile b/drivers/base/regmap/Makefile
    > index 11facb32a027..504a32b79d8c 100644
    > --- a/drivers/base/regmap/Makefile
    > +++ b/drivers/base/regmap/Makefile
    > @@ -20,3 +20,4 @@ obj-$(CONFIG_REGMAP_SCCB) += regmap-sccb.o
    > obj-$(CONFIG_REGMAP_I3C) += regmap-i3c.o
    > obj-$(CONFIG_REGMAP_SPI_AVMM) += regmap-spi-avmm.o
    > obj-$(CONFIG_REGMAP_MDIO) += regmap-mdio.o
    > +obj-$(CONFIG_REGMAP_INDIRECT_REGISTER) += regmap-indirect-register.o
    > diff --git a/drivers/base/regmap/regmap-indirect-register.c b/drivers/base/regmap/regmap-indirect-register.c
    > new file mode 100644
    > index 000000000000..0b748e48bd87
    > --- /dev/null
    > +++ b/drivers/base/regmap/regmap-indirect-register.c
    > @@ -0,0 +1,133 @@
    > +// SPDX-License-Identifier: GPL-2.0
    > +//
    > +// Indirect Register Access.
    > +//
    > +// Copyright (C) 2022 Intel Corporation, Inc.
    > +
    > +#include <linux/device.h>
    > +#include <linux/module.h>
    > +#include <linux/regmap.h>
    > +
    > +#define INDIRECT_CMD_OFF 0x0
    > +#define INDIRECT_CMD_RD BIT(0)
    > +#define INDIRECT_CMD_WR BIT(1)
    > +#define INDIRECT_CMD_ACK BIT(2)
    > +
    > +#define INDIRECT_ADDR_OFF 0x4
    > +#define INDIRECT_RD_OFF 0x8
    > +#define INDIRECT_WR_OFF 0xc
    > +
    > +#define INDIRECT_INT_US 1
    > +#define INDIRECT_TIMEOUT_US 10000
    > +
    > +struct indirect_ctx {
    > + void __iomem *base;
    > + struct device *dev;
    > +};
    > +
    > +static int indirect_bus_clr_cmd(struct indirect_ctx *ctx)
    > +{
    > + unsigned int cmd;
    > + int ret;
    > +
    > + writel(0, ctx->base + INDIRECT_CMD_OFF);
    > + ret = readl_poll_timeout((ctx->base + INDIRECT_CMD_OFF), cmd,
    > + (!cmd), INDIRECT_INT_US, INDIRECT_TIMEOUT_US);
    > + if (ret)
    > + dev_err(ctx->dev, "%s timed out on clearing cmd 0x%xn", __func__, cmd);
    The line-return in the above dev_err() is missing a forward slash: \n

    - Russ
    > +
    > + return ret;
    > +}
    > +
    > +static int indirect_bus_reg_read(void *context, unsigned int reg,
    > + unsigned int *val)
    > +{
    > + struct indirect_ctx *ctx = context;
    > + unsigned int cmd;
    > + int ret;
    > +
    > + cmd = readl(ctx->base + INDIRECT_CMD_OFF);
    > + if (cmd)
    > + dev_warn(ctx->dev, "%s non-zero cmd 0x%x\n", __func__, cmd);
    > +
    > + writel(reg, ctx->base + INDIRECT_ADDR_OFF);
    > + writel(INDIRECT_CMD_RD, ctx->base + INDIRECT_CMD_OFF);
    > + ret = readl_poll_timeout((ctx->base + INDIRECT_CMD_OFF), cmd,
    > + (cmd & INDIRECT_CMD_ACK), INDIRECT_INT_US,
    > + INDIRECT_TIMEOUT_US);
    > + if (ret) {
    > + dev_err(ctx->dev, "%s timed out on reg 0x%x cmd 0x%x\n", __func__, reg, cmd);
    > + goto out;
    > + }
    > +
    > + *val = readl(ctx->base + INDIRECT_RD_OFF);
    > +
    > + if (indirect_bus_clr_cmd(ctx))
    > + ret = -ETIMEDOUT;
    > +
    > +out:
    > + return ret;
    > +}
    > +
    > +static int indirect_bus_reg_write(void *context, unsigned int reg,
    > + unsigned int val)
    > +{
    > + struct indirect_ctx *ctx = context;
    > + unsigned int cmd;
    > + int ret;
    > +
    > + cmd = readl(ctx->base + INDIRECT_CMD_OFF);
    > + if (cmd)
    > + dev_warn(ctx->dev, "%s non-zero cmd 0x%x\n", __func__, cmd);
    > +
    > + writel(val, ctx->base + INDIRECT_WR_OFF);
    > + writel(reg, ctx->base + INDIRECT_ADDR_OFF);
    > + writel(INDIRECT_CMD_WR, ctx->base + INDIRECT_CMD_OFF);
    > + ret = readl_poll_timeout((ctx->base + INDIRECT_CMD_OFF), cmd,
    > + (cmd & INDIRECT_CMD_ACK), INDIRECT_INT_US,
    > + INDIRECT_TIMEOUT_US);
    > + if (ret) {
    > + dev_err(ctx->dev, "%s timed out on reg 0x%x cmd 0x%x\n", __func__, reg, cmd);
    > + goto out;
    > + }
    > +
    > + if (indirect_bus_clr_cmd(ctx))
    > + ret = -ETIMEDOUT;
    > +
    > +out:
    > + return ret;
    > +}
    > +
    > +static const struct regmap_bus indirect_bus = {
    > + .reg_write = indirect_bus_reg_write,
    > + .reg_read = indirect_bus_reg_read,
    > +};
    > +
    > +/**
    > + * devm_regmap_init_indirect_register - create a regmap for indirect register access
    > + * @dev: device creating the regmap
    > + * @base: __iomem point to base of memory with mailbox
    > + * @cfg: regmap_config describing interface
    > + *
    > + * Return: 0 on success, negative error code otherwise.
    > + */
    > +struct regmap *devm_regmap_init_indirect_register(struct device *dev,
    > + void __iomem *base,
    > + struct regmap_config *cfg)
    > +{
    > + struct indirect_ctx *ctx;
    > +
    > + ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
    > + if (!ctx)
    > + return NULL;
    > +
    > + ctx->base = base;
    > + ctx->dev = dev;
    > +
    > + return devm_regmap_init(dev, &indirect_bus, ctx, cfg);
    > +}
    > +EXPORT_SYMBOL_GPL(devm_regmap_init_indirect_register);
    > +
    > +MODULE_DESCRIPTION("Indirect Register Access");
    > +MODULE_AUTHOR("Intel Corporation");
    > +MODULE_LICENSE("GPL");
    > diff --git a/include/linux/regmap.h b/include/linux/regmap.h
    > index de81a94d7b30..72eb38883e88 100644
    > --- a/include/linux/regmap.h
    > +++ b/include/linux/regmap.h
    > @@ -670,6 +670,18 @@ struct regmap *__devm_regmap_init_spi_avmm(struct spi_device *spi,
    > const struct regmap_config *config,
    > struct lock_class_key *lock_key,
    > const char *lock_name);
    > +/**
    > + * devm_regmap_init_indirect_register - create a regmap for indirect register access
    > + * @dev: device creating the regmap
    > + * @base: __iomem point to base of memory with mailbox
    > + * @cfg: regmap_config describing interface
    > + *
    > + * Return: 0 on success, negative error code otherwise.
    > + */
    > +struct regmap *devm_regmap_init_indirect_register(struct device *dev,
    > + void __iomem *base,
    > + struct regmap_config *cfg);
    > +
    > /*
    > * Wrapper for regmap_init macros to include a unique lockdep key and name
    > * for each call. No-op if CONFIG_LOCKDEP is not set.

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