Re: [PATCH 1/1] mfd: Add I2C based System Configuaration (SYSCON) access

[Lee Jones]

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@xxxxxxxxxx>
> ---
>  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@xxxxxxxxxx>
> + */
> +
> +#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@xxxxxxxxxx>
> + */
> +
> +#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 [æçæ]
Senior Technical Lead - Developer Services
Linaro.org â Open source software for Arm SoCs
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