Re: [PATCH v2 1/4] power: supply: add support for max77759 fuel gauge

[Dimitri Fedrau <dima.fedrau@gmail.com>]

Hi Thomas,

Am Thu, Jan 02, 2025 at 12:15:03PM +0100 schrieb Thomas Antoine via B4 Relay:
> From: Thomas Antoine <t.antoine@uclouvain.be>
> 
> The interface of the Maxim max77759 fuel gauge has a lot of common with the
> Maxim max1720x. The major difference is the lack of non-volatile memory
> slave address. No slave is available at address 0xb of the i2c bus, which
> is coherent with the following driver from google: line 5836 disables
> non-volatile memory for m5 gauge.
> 
> Link: https://android.googlesource.com/kernel/google-modules/bms/+/1a68c36bef474573cc8629cc1d121eb6a81ab68c/max1720x_battery.c
> 
> Other differences include the lack of V_BATT register to read the battery
> level and a difference in the way to identify the chip (the same register
> is used but not the same mask).
> 
> Add support for the max77759 by allowing to use the non-volatile
> memory or not based on the chip. Also add the V_CELL regsister as a
> fallback to read voltage value in the case where read of V_BATT fails.
> 
> The cast is necessary to avoid an overflow when the value of the register
> is above 54975 (equivalent to a voltage around 4.29 V).
> 
> The regmap of the max77759 will lead the read to fail for V_BATT and to
> correctly use V_CELL instead. This regmap was proposed by André Draszik in
> 
> Link: https://lore.kernel.org/all/d1bade77b5281c1de6b2ddcb4dbbd033e455a116.camel@linaro.org/
> 
> Signed-off-by: Thomas Antoine <t.antoine@uclouvain.be>
> ---
>  drivers/power/supply/max1720x_battery.c | 189 +++++++++++++++++++++++++++-----
>  1 file changed, 164 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/power/supply/max1720x_battery.c b/drivers/power/supply/max1720x_battery.c
> index 33105419e2427bb37963bda9948b647c239f8faa..a41976679eded44fbd13120ad756a626d2867919 100644
> --- a/drivers/power/supply/max1720x_battery.c
> +++ b/drivers/power/supply/max1720x_battery.c
> @@ -27,6 +27,7 @@
>  #define MAX172XX_REPCAP			0x05	/* Average capacity */
>  #define MAX172XX_REPSOC			0x06	/* Percentage of charge */
>  #define MAX172XX_TEMP			0x08	/* Temperature */
> +#define MAX172XX_VCELL			0x09	/* Lowest cell voltage */
>  #define MAX172XX_CURRENT		0x0A	/* Actual current */
>  #define MAX172XX_AVG_CURRENT		0x0B	/* Average current */
>  #define MAX172XX_TTE			0x11	/* Time to empty */
> @@ -39,6 +40,8 @@
>  #define MAX172XX_DEV_NAME_TYPE_MASK	GENMASK(3, 0)
>  #define MAX172XX_DEV_NAME_TYPE_MAX17201	BIT(0)
>  #define MAX172XX_DEV_NAME_TYPE_MAX17205	(BIT(0) | BIT(2))
> +#define MAX77759_DEV_NAME_TYPE_MASK	GENMASK(15, 9)
> +#define MAX77759_DEV_NAME_TYPE_MAX77759	0x31
>  #define MAX172XX_QR_TABLE10		0x22
>  #define MAX172XX_BATT			0xDA	/* Battery voltage */
>  #define MAX172XX_ATAVCAP		0xDF
> @@ -46,12 +49,20 @@
>  static const char *const max1720x_manufacturer = "Maxim Integrated";
>  static const char *const max17201_model = "MAX17201";
>  static const char *const max17205_model = "MAX17205";
> +static const char *const max77759_model = "MAX77759";
> +
> +enum chip_id {
> +	MAX1720X_ID,
> +	MAX77759_ID,
> +};
>  
>  struct max1720x_device_info {
>  	struct regmap *regmap;
>  	struct regmap *regmap_nv;
>  	struct i2c_client *ancillary;
>  	int rsense;
> +	int has_nvmem;

Switch to bool and why is needed twice ? Here and in chip_data. Better
keep it in chip_data.

> +	enum chip_id id;
>  };
>  
>  /*
> @@ -254,6 +265,67 @@ static const enum power_supply_property max1720x_battery_props[] = {
>  	POWER_SUPPLY_PROP_MANUFACTURER,
>  };
>  
> +/*
> + * Registers 0x80 up to 0xaf which contain the model for the fuel gauge
> + * algorithm (stored in nvmem for the max1720x) are locked. They can
> + * be unlocked by writing 0x59 to 0x62 and 0xc4 to 0x63. They should be
> + * enabled in the regmap if the driver is extended to manage the model.
> + */
> +static const struct regmap_range max77759_registers[] = {
> +	regmap_reg_range(0x00, 0x4f),
> +	regmap_reg_range(0xb0, 0xbf),
> +	regmap_reg_range(0xd0, 0xd0),
> +	regmap_reg_range(0xdc, 0xdf),
> +	regmap_reg_range(0xfb, 0xfb),
> +	regmap_reg_range(0xff, 0xff),
> +};
> +
> +static const struct regmap_range max77759_ro_registers[] = {
> +	regmap_reg_range(0x3d, 0x3d),
> +	regmap_reg_range(0xfb, 0xfb),
> +	regmap_reg_range(0xff, 0xff),
> +};
> +
> +static const struct regmap_access_table max77759_write_table = {
> +	.yes_ranges = max77759_registers,
> +	.n_yes_ranges = ARRAY_SIZE(max77759_registers),
> +	.no_ranges = max77759_ro_registers,
> +	.n_no_ranges = ARRAY_SIZE(max77759_ro_registers),
> +};
> +
> +static const struct regmap_access_table max77759_rd_table = {
> +	.yes_ranges = max77759_registers,
> +	.n_yes_ranges = ARRAY_SIZE(max77759_registers),
> +};
> +
> +static const struct regmap_config max77759_regmap_cfg = {
> +	.reg_bits = 8,
> +	.val_bits = 16,
> +	.max_register = 0xff,
> +	.wr_table = &max77759_write_table,
> +	.rd_table = &max77759_rd_table,
> +	.val_format_endian = REGMAP_ENDIAN_LITTLE,
> +	.cache_type = REGCACHE_NONE,
> +};
> +
> +struct chip_data {
> +	u8 has_nvmem;
> +	const struct regmap_config *regmap_cfg;
> +	enum chip_id id;
> +};
> +
> +static const struct chip_data max1720x_data  = {
> +	.has_nvmem = 1,
> +	.regmap_cfg = &max1720x_regmap_cfg,
> +	.id = MAX1720X_ID,
> +};
> +
> +static const struct chip_data max77759_data = {
> +	.has_nvmem = 0,
> +	.regmap_cfg = &max77759_regmap_cfg,
> +	.id = MAX77759_ID,
> +};
> +
>  /* Convert regs value to power_supply units */
>  
>  static int max172xx_time_to_ps(unsigned int reg)
> @@ -271,6 +343,14 @@ static int max172xx_voltage_to_ps(unsigned int reg)
>  	return reg * 1250;	/* in uV */
>  }
>  
> +// Use 64 bits because computation on 32 bits leads to an overflow
> +static int max172xx_cell_voltage_to_ps(unsigned int reg)
> +{
> +	u64 val = reg;
> +
> +	return val * 78125 / 1000;	/* in uV */

You could avoid the overflow with:
	return val * 625 / 8;	/* in uV */
> +}
> +
>  static int max172xx_capacity_to_ps(unsigned int reg)
>  {
>  	return reg * 500;	/* in uAh */
> @@ -303,6 +383,33 @@ static int max172xx_current_to_voltage(unsigned int reg)
>  	return val * 156252;
>  }
>  
> +static int max1720x_devname_to_model(unsigned int reg_val,
> +					union power_supply_propval *val,
> +					struct max1720x_device_info *info)

nit: Align with open parenthesis

> +{
> +	switch (info->id) {
> +	case MAX1720X_ID:
> +		reg_val = FIELD_GET(MAX172XX_DEV_NAME_TYPE_MASK, reg_val);
> +		if (reg_val == MAX172XX_DEV_NAME_TYPE_MAX17201)
> +			val->strval = max17201_model;
> +		else if (reg_val == MAX172XX_DEV_NAME_TYPE_MAX17205)
> +			val->strval = max17205_model;
> +		else
> +			return -ENODEV;
> +		break;
> +	case MAX77759_ID:
> +		reg_val = FIELD_GET(MAX77759_DEV_NAME_TYPE_MASK, reg_val);
> +		if (reg_val == MAX77759_DEV_NAME_TYPE_MAX77759)
> +			val->strval = max77759_model;
> +		else
> +			return -ENODEV;
> +		break;
> +	default:
> +		return -ENODEV;
> +	}
> +	return 0;
> +}
> +
>  static int max1720x_battery_get_property(struct power_supply *psy,
>  					 enum power_supply_property psp,
>  					 union power_supply_propval *val)
> @@ -332,7 +439,12 @@ static int max1720x_battery_get_property(struct power_supply *psy,
>  		break;
>  	case POWER_SUPPLY_PROP_VOLTAGE_NOW:
>  		ret = regmap_read(info->regmap, MAX172XX_BATT, &reg_val);
> -		val->intval = max172xx_voltage_to_ps(reg_val);
> +		if (!ret)
> +			val->intval = max172xx_voltage_to_ps(reg_val);
> +		else {
> +			ret = regmap_read(info->regmap, MAX172XX_VCELL, &reg_val);
> +			val->intval = max172xx_cell_voltage_to_ps(reg_val);
> +		}

Would be better to read the right register, since we know which device
we are. You could differentiate like in max1720x_devname_to_model.

>  		break;
>  	case POWER_SUPPLY_PROP_CHARGE_FULL_DESIGN:
>  		ret = regmap_read(info->regmap, MAX172XX_DESIGN_CAP, &reg_val);
> @@ -364,13 +476,8 @@ static int max1720x_battery_get_property(struct power_supply *psy,
>  		break;
>  	case POWER_SUPPLY_PROP_MODEL_NAME:
>  		ret = regmap_read(info->regmap, MAX172XX_DEV_NAME, &reg_val);
> -		reg_val = FIELD_GET(MAX172XX_DEV_NAME_TYPE_MASK, reg_val);
> -		if (reg_val == MAX172XX_DEV_NAME_TYPE_MAX17201)
> -			val->strval = max17201_model;
> -		else if (reg_val == MAX172XX_DEV_NAME_TYPE_MAX17205)
> -			val->strval = max17205_model;
> -		else
> -			return -ENODEV;
> +		if (!ret)
> +			ret = max1720x_devname_to_model(reg_val, val, info);
>  		break;
>  	case POWER_SUPPLY_PROP_MANUFACTURER:
>  		val->strval = max1720x_manufacturer;
> @@ -416,7 +523,6 @@ static int max1720x_probe_nvmem(struct i2c_client *client,
>  		.priv = info,
>  	};
>  	struct nvmem_device *nvmem;
> -	unsigned int val;
>  	int ret;
>  
>  	info->ancillary = i2c_new_ancillary_device(client, "nvmem", 0xb);
> @@ -438,18 +544,6 @@ static int max1720x_probe_nvmem(struct i2c_client *client,
>  		return PTR_ERR(info->regmap_nv);
>  	}
>  
> -	ret = regmap_read(info->regmap_nv, MAX1720X_NRSENSE, &val);
> -	if (ret < 0) {
> -		dev_err(dev, "Failed to read sense resistor value\n");
> -		return ret;
> -	}
> -
> -	info->rsense = val;
> -	if (!info->rsense) {
> -		dev_warn(dev, "RSense not calibrated, set 10 mOhms!\n");
> -		info->rsense = 1000; /* in regs in 10^-5 */
> -	}
> -
>  	nvmem = devm_nvmem_register(dev, &nvmem_config);
>  	if (IS_ERR(nvmem)) {
>  		dev_err(dev, "Could not register nvmem!");
> @@ -459,6 +553,36 @@ static int max1720x_probe_nvmem(struct i2c_client *client,
>  	return 0;
>  }
>  
> +static int max1720x_get_rsense(struct device *dev,
> +					 struct max1720x_device_info *info)

nit: Align with open parenthesis.

> +{
> +	unsigned int val;
> +	int ret;
> +
> +	if (info->has_nvmem) {
> +		ret = regmap_read(info->regmap_nv, MAX1720X_NRSENSE, &val);
> +		if (ret < 0) {
> +			dev_err(dev, "Failed to read RSense from nvmem\n");
> +			return ret;
> +		}
> +
> +		info->rsense = val;
> +		if (!info->rsense) {
> +			dev_warn(dev, "RSense not calibrated, set 10 mOhms!\n");
> +			info->rsense = 1000; /* in regs in 10^-5 */
> +		}
> +	} else {
> +		ret = of_property_read_u32(dev->of_node,
> +					"shunt-resistor-micro-ohms", &val);

nit: Align with open parenthesis.

> +		if (ret) {
> +			dev_err(dev, "Failed to read RSense from devicetree\n");
> +			return ret;
> +		}
> +		info->rsense = val/10;
> +	}
> +	return 0;
> +}
> 
[...]

Best regards,
Dimitri Fedrau