Re: [PATCH v8 4/8] mfd: khadas-mcu: Add support for VIM4 MCU variant

[Lee Jones <lee@kernel.org>]

/* Sashiko Automation: Reviewed (0 Findings) */

On Thu, 02 Jul 2026, Ronald Claveau via B4 Relay wrote:

> From: Ronald Claveau <linux-kernel-dev@aliel.fr>
> 
> Refactor probe() to use per-variant values
> instead of hardcoded globals.
> 
> Add dedicated regmap configuration for the VIM4 MCU,
> with its own volatile/writeable registers.
> 
> Add the fan control register
> (0–100 levels vs 0–3 for previous supported boards).
> 
> Add a new compatible string "khadas,vim4-mcu".
> 
> Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
> Signed-off-by: Ronald Claveau <linux-kernel-dev@aliel.fr>
> ---
> 
>  drivers/mfd/khadas-mcu.c | 118 ++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 102 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/mfd/khadas-mcu.c b/drivers/mfd/khadas-mcu.c
> index ba981a7886921..d2ca7deda45c6 100644
> --- a/drivers/mfd/khadas-mcu.c
> +++ b/drivers/mfd/khadas-mcu.c
> @@ -13,6 +13,9 @@
>  #include <linux/module.h>
>  #include <linux/regmap.h>
>  
> #define KHADAS_MCU_FAN_LEVEL_MAX 3
> #define KHADAS_MCU_VIM4_FAN_LEVEL_MAX 0x64
> +
>  static bool khadas_mcu_reg_volatile(struct device *dev, unsigned int reg)
>  {
>  	if (reg >= KHADAS_MCU_USER_DATA_0_REG &&
> @@ -75,47 +78,129 @@ static const struct regmap_config khadas_mcu_regmap_config = {
>  	.cache_type	= REGCACHE_MAPLE,
>  };
>  
> -static struct mfd_cell khadas_mcu_fan_cells[] = {
> +static const struct khadas_mcu_fan_pdata khadas_mcu_fan_pdata = {
> +	.fan_reg	= KHADAS_MCU_CMD_FAN_STATUS_CTRL_REG,
> +	.max_level	= KHADAS_MCU_FAN_LEVEL_MAX,
> +};
> +
> +static const struct mfd_cell khadas_mcu_fan_cells[] = {
>  	/* VIM1/2 Rev13+ and VIM3 only */
> -	{ .name = "khadas-mcu-fan-ctrl", },
> +	{
> +		.name = "khadas-mcu-fan-ctrl",
> +		.platform_data = &khadas_mcu_fan_pdata,
> +		.pdata_size = sizeof(khadas_mcu_fan_pdata),
> +	},
>  };

If you're tweaking, feel free to get more upstream creds by laying down
a prelim patch changing these to MFD_CELL_*().

> -static struct mfd_cell khadas_mcu_cells[] = {
> +static const struct mfd_cell khadas_mcu_cells[] = {
>  	{ .name = "khadas-mcu-user-mem", },
>  };
>  
> +static bool khadas_mcu_vim4_reg_volatile(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case KHADAS_MCU_PWR_OFF_CMD_REG:
> +	case KHADAS_MCU_VIM4_REST_CONF_REG:
> +	case KHADAS_MCU_WOL_INIT_START_REG:
> +	case KHADAS_MCU_VIM4_LED_ON_RAM_REG:
> +	case KHADAS_MCU_VIM4_FAN_CTRL_REG:
> +	case KHADAS_MCU_VIM4_WDT_EN_REG:
> +	case KHADAS_MCU_VIM4_SYS_RST_REG:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +
> +static bool khadas_mcu_vim4_reg_writeable(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case KHADAS_MCU_VERSION_0_REG:
> +	case KHADAS_MCU_VERSION_1_REG:
> +	case KHADAS_MCU_SHUTDOWN_NORMAL_STATUS_REG:
> +		return false;
> +	default:
> +		return true;
> +	}
> +}
> +
> +static const struct regmap_config khadas_mcu_vim4_regmap_config = {
> +	.reg_bits	= 8,
> +	.reg_stride	= 1,
> +	.val_bits	= 8,
> +	.max_register	= KHADAS_MCU_VIM4_SYS_RST_REG,
> +	.volatile_reg	= khadas_mcu_vim4_reg_volatile,
> +	.writeable_reg	= khadas_mcu_vim4_reg_writeable,
> +	.cache_type	= REGCACHE_MAPLE,
> +};
> +
> +static const struct khadas_mcu_fan_pdata khadas_vim4_fan_pdata = {
> +	.fan_reg	= KHADAS_MCU_VIM4_FAN_CTRL_REG,
> +	.max_level	= KHADAS_MCU_VIM4_FAN_LEVEL_MAX,
> +};
> +
> +static const struct mfd_cell khadas_mcu_vim4_cells[] = {
> +	{
> +		.name		= "khadas-mcu-fan-ctrl",
> +		.platform_data	= &khadas_vim4_fan_pdata,
> +		.pdata_size	= sizeof(khadas_vim4_fan_pdata),
> +	},
> +};
> +
>  static int khadas_mcu_probe(struct i2c_client *client)
>  {
> +	const struct mfd_cell *cells, *fan_cells;
> +	const struct regmap_config *regmap_cfg;
>  	struct device *dev = &client->dev;
> +	int ncells, nfan_cells, ret;
>  	struct khadas_mcu *ddata;
> -	int ret;
>  
>  	ddata = devm_kzalloc(dev, sizeof(*ddata), GFP_KERNEL);
>  	if (!ddata)
>  		return -ENOMEM;
>  
> +	switch ((uintptr_t)i2c_get_match_data(client)) {

Let's pull this out of the switch():

	const void *match;

	match = i2c_get_match_data(client);
	if (!match)
		return -ENODEV;

This would separate the declaration from the potentially failing
function call and prevent implicitly matching 'KHADAS_MCU_GENERIC' (if
its value is 0) should the lookup fail.

> +	case KHADAS_MCU_GENERIC:
> +		regmap_cfg	= &khadas_mcu_regmap_config;
> +		cells		= khadas_mcu_cells;
> +		ncells		= ARRAY_SIZE(khadas_mcu_cells);
> +		fan_cells	= khadas_mcu_fan_cells;
> +		nfan_cells	= ARRAY_SIZE(khadas_mcu_fan_cells);
> +		break;
> +	case KHADAS_MCU_VIM4:
> +		regmap_cfg	= &khadas_mcu_vim4_regmap_config;
> +		cells		= NULL;
> +		ncells		= 0;
> +		fan_cells	= khadas_mcu_vim4_cells;
> +		nfan_cells	= ARRAY_SIZE(khadas_mcu_vim4_cells);
> +		break;
> +	default:
> +		return -ENODEV;
> +	}
> +
>  	i2c_set_clientdata(client, ddata);
>  
>  	ddata->dev = dev;
>  
> -	ddata->regmap = devm_regmap_init_i2c(client, &khadas_mcu_regmap_config);
> +	ddata->regmap = devm_regmap_init_i2c(client, regmap_cfg);
>  	if (IS_ERR(ddata->regmap)) {
>  		ret = PTR_ERR(ddata->regmap);
> -		dev_err(dev, "Failed to allocate register map: %d\n", ret);
> -		return ret;
> +		return dev_err_probe(dev, ret, "Failed to allocate register map\n");
>  	}
>  
> -	ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
> -				   khadas_mcu_cells,
> -				   ARRAY_SIZE(khadas_mcu_cells),
> -				   NULL, 0, NULL);
> -	if (ret)
> -		return ret;
> +	if (cells && ncells) {
> +		ret = devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
> +					   cells,
> +					   ncells,
> +					   NULL, 0, NULL);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	if (of_property_present(dev->of_node, "#cooling-cells"))
>  		return devm_mfd_add_devices(dev, PLATFORM_DEVID_NONE,
> -					    khadas_mcu_fan_cells,
> -					    ARRAY_SIZE(khadas_mcu_fan_cells),
> +					    fan_cells,
> +					    nfan_cells,
>  					    NULL, 0, NULL);
>  
>  	return 0;
> @@ -123,7 +208,8 @@ static int khadas_mcu_probe(struct i2c_client *client)
>  
>  #ifdef CONFIG_OF
>  static const struct of_device_id khadas_mcu_of_match[] = {
> -	{ .compatible = "khadas,mcu", },
> +	{ .compatible = "khadas,mcu", .data = (void *)KHADAS_MCU_GENERIC },
> +	{ .compatible = "khadas,vim4-mcu", .data = (void *)KHADAS_MCU_VIM4 },
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, khadas_mcu_of_match);
> 
> -- 
> 2.49.0
> 
> 

-- 
Lee Jones