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    SubjectRe: [PATCH 1/1] mfd: Add I2C based System Configuaration (SYSCON) access
    On Tue, 16 Jun 2020, Lee Jones wrote:

    > The existing SYSCON implementation only supports MMIO (memory mapped)
    > accesses, facilitated by Regmap. This extends support for registers
    > held behind I2C busses.
    >
    > Signed-off-by: Lee Jones <lee.jones@linaro.org>
    > ---
    > drivers/mfd/Kconfig | 7 +++
    > drivers/mfd/Makefile | 1 +
    > drivers/mfd/syscon-i2c.c | 89 ++++++++++++++++++++++++++++++++++
    > include/linux/mfd/syscon-i2c.h | 26 ++++++++++
    > 4 files changed, 123 insertions(+)
    > create mode 100644 drivers/mfd/syscon-i2c.c
    > create mode 100644 include/linux/mfd/syscon-i2c.h
    >
    > diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
    > index 0a59249198d34..63ae78b92b086 100644
    > --- a/drivers/mfd/Kconfig
    > +++ b/drivers/mfd/Kconfig
    > @@ -1300,6 +1300,13 @@ config MFD_SYSCON
    > Select this option to enable accessing system control registers
    > via regmap.
    >
    > +config MFD_SYSCON_I2C
    > + bool "System Controller Register R/W Based on I2C Regmap"
    > + select REGMAP_I2C
    > + help
    > + Select this option to enable accessing system control registers
    > + via I2C using regmap.
    > +
    > config MFD_DAVINCI_VOICECODEC
    > tristate
    > select MFD_CORE
    > diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
    > index f935d10cbf0fc..0aec1f42ac979 100644
    > --- a/drivers/mfd/Makefile
    > +++ b/drivers/mfd/Makefile
    > @@ -219,6 +219,7 @@ obj-$(CONFIG_MFD_RK808) += rk808.o
    > obj-$(CONFIG_MFD_RN5T618) += rn5t618.o
    > obj-$(CONFIG_MFD_SEC_CORE) += sec-core.o sec-irq.o
    > obj-$(CONFIG_MFD_SYSCON) += syscon.o
    > +obj-$(CONFIG_MFD_SYSCON_I2C) += syscon-i2c.o
    > obj-$(CONFIG_MFD_LM3533) += lm3533-core.o lm3533-ctrlbank.o
    > obj-$(CONFIG_MFD_VEXPRESS_SYSREG) += vexpress-sysreg.o
    > obj-$(CONFIG_MFD_RETU) += retu-mfd.o
    > diff --git a/drivers/mfd/syscon-i2c.c b/drivers/mfd/syscon-i2c.c
    > new file mode 100644
    > index 0000000000000..404e595d7646c
    > --- /dev/null
    > +++ b/drivers/mfd/syscon-i2c.c
    > @@ -0,0 +1,89 @@
    > +// SPDX-License-Identifier: GPL-2.0-or-later
    > +/*
    > + * System Control Driver accessed over I2C
    > + *
    > + * Copyright (C) 2020 Linaro Ltd.
    > + *
    > + * Author: Lee Jones <lee.jones@linaro.org>
    > + */
    > +
    > +#include <linux/err.h>
    > +#include <linux/i2c.h>
    > +#include <linux/list.h>
    > +#include <linux/mfd/syscon-i2c.h>
    > +#include <linux/regmap.h>
    > +
    > +static DEFINE_SPINLOCK(syscon_i2c_list_slock);
    > +static LIST_HEAD(syscon_i2c_list);
    > +
    > +struct syscon {
    > + struct device_node *np;

    Note to self: struct i2c_client *client;

    > + struct regmap *regmap;
    > + struct list_head list;
    > +};
    > +
    > +static const struct regmap_config syscon_i2c_regmap_config = {
    > + .reg_bits = 8,
    > + .val_bits = 8,
    > +};
    > +
    > +static struct syscon *of_syscon_i2c_register(struct i2c_client *client)
    > +{
    > + struct regmap_config syscon_config = syscon_i2c_regmap_config;
    > + struct device_node *np = client->dev.of_node;
    > + struct syscon *syscon;
    > + struct regmap *regmap;
    > + int ret;
    > +
    > + syscon = devm_kzalloc(&client->dev, sizeof(*syscon), GFP_KERNEL);
    > + if (!syscon)
    > + return ERR_PTR(-ENOMEM);
    > +
    > + syscon_config.name = of_node_full_name(np);

    Note to self: Use dev_name();

    > + regmap = devm_regmap_init_i2c(client, &syscon_config);
    > + if (IS_ERR(regmap)) {
    > + dev_err(&client->dev, "Failed to initialise Regmap I2C\n");
    > + ret = PTR_ERR(regmap);
    > + return ERR_PTR(ret);
    > + }
    > +
    > + syscon->regmap = regmap;
    > + syscon->np = np;
    > +
    > + spin_lock(&syscon_i2c_list_slock);
    > + list_add_tail(&syscon->list, &syscon_i2c_list);
    > + spin_unlock(&syscon_i2c_list_slock);
    > +
    > + return syscon;
    > +}
    > +
    > +static struct regmap *i2c_device_node_get_regmap(struct i2c_client *client)

    Note to self: i2c_client_get_regmap()

    > +{
    > + struct device_node *np = client->dev.of_node;
    > + struct syscon *entry, *syscon = NULL;
    > +
    > + spin_lock(&syscon_i2c_list_slock);
    > +
    > + list_for_each_entry(entry, &syscon_i2c_list, list)
    > + if (entry->np == np) {
    > + syscon = entry;
    > + break;
    > + }
    > +
    > + spin_unlock(&syscon_i2c_list_slock);
    > +
    > + if (!syscon)
    > + syscon = of_syscon_i2c_register(client);
    > +
    > + if (IS_ERR(syscon))
    > + return ERR_CAST(syscon);
    > +
    > + return syscon->regmap;
    > +}
    > +
    > +struct regmap *i2c_device_node_to_regmap(struct i2c_client *client)

    Note to self: i2c_client_to_regmap()

    > +{
    > + return i2c_device_node_get_regmap(client);
    > +}
    > +EXPORT_SYMBOL_GPL(i2c_device_node_to_regmap);
    > diff --git a/include/linux/mfd/syscon-i2c.h b/include/linux/mfd/syscon-i2c.h
    > new file mode 100644
    > index 0000000000000..854e316fec93e
    > --- /dev/null
    > +++ b/include/linux/mfd/syscon-i2c.h
    > @@ -0,0 +1,26 @@
    > +/* SPDX-License-Identifier: GPL-2.0-or-later */
    > +/*
    > + * System Control Driver accessed via I2C
    > + *
    > + * Copyright (C) 2020 Linaro Ltd.
    > + *
    > + * Author: Lee Jones <lee.jones@linaro.org>
    > + */
    > +
    > +#ifndef __LINUX_MFD_SYSCON_I2C_H__
    > +#define __LINUX_MFD_SYSCON_I2C_H__
    > +
    > +#include <linux/err.h>
    > +#include <linux/errno.h>
    > +#include <linux/i2c.h>
    > +
    > +#ifdef CONFIG_MFD_SYSCON_I2C
    > +extern struct regmap *i2c_device_node_to_regmap(struct i2c_client *client);
    > +#else
    > +static inline struct regmap *i2c_device_node_to_regmap(struct i2c_client *client)
    > +{
    > + return ERR_PTR(-ENOTSUPP);
    > +}
    > +#endif
    > +
    > +#endif /* __LINUX_MFD_SYSCON_I2C_H__ */

    --
    Lee Jones [李琼斯]
    Senior Technical Lead - Developer Services
    Linaro.org │ Open source software for Arm SoCs
    Follow Linaro: Facebook | Twitter | Blog

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