Re: [PATCH v7 2/4] power: supply: Add support for the Qualcomm Battery Monitoring System

[Sebastian Reichel]

Hi,

First of all thanks for the patch and big sorry for the long delay
in reviewing this. I did not find enough time to do it properly
until now :(

On Thu, Jun 14, 2018 at 04:14:15PM +0100, Craig Tatlor wrote:
> This patch adds a driver for the BMS (Battery Monitoring System)
> block of the PM8941 PMIC, it uses a lookup table defined in the
> device tree to generate a capacity from the BMS supplied OCV, it
> then amends the coulomb counter to that to increase the accuracy
> of the estimated capacity.
> 
> Signed-off-by: Craig Tatlor <ctatlor97@xxxxxxxxx>
> Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
> 
> * Changes from v5:                                                                                                                                                                                                   
>   Uses select for REGMAP_SPMI.                                                                                                                                                                                       
>                                                                                                                                                                                                                      
> * Changes from v4:                                                                                                                                                                                                   
>   Cleaned up percentage interpolation function,                                                                                                                                                                      
>   uses new fixp interpolation helper,                                                                                                                                                                                
>   added some more error cases,                                                                                                                                                                                       
>   uses devm_power_supply_register(),                                                                                                                                                                                 
>   uses a DIV_ROUND_CLOSEST for division and                                                                                                                                                                          
>   uses micro(volts / amp hours) instead of                                                                                                                                                                           
>   milli (volts / amp hours).  
> 
>  drivers/power/supply/Kconfig    |   9 +
>  drivers/power/supply/Makefile   |   1 +
>  drivers/power/supply/qcom_bms.c | 487 ++++++++++++++++++++++++++++++++
>  3 files changed, 497 insertions(+)
>  create mode 100644 drivers/power/supply/qcom_bms.c
> 
> diff --git a/drivers/power/supply/Kconfig b/drivers/power/supply/Kconfig
> index 428b426842f4..75f2f375f992 100644
> --- a/drivers/power/supply/Kconfig
> +++ b/drivers/power/supply/Kconfig
> @@ -82,6 +82,15 @@ config BATTERY_ACT8945A
>  	  Say Y here to enable support for power supply provided by
>  	  Active-semi ActivePath ACT8945A charger.
>  
> +config BATTERY_BMS
> +	tristate "Qualcomm Battery Monitoring System driver"
> +	depends on MFD_SPMI_PMIC || COMPILE_TEST
> +	depends on OF
> +	select REGMAP_SPMI
> +	help
> +	  Say Y to include support for the Battery Monitoring hardware
> +	  found in some Qualcomm PM series PMICs.
> +
>  config BATTERY_CPCAP
>  	tristate "Motorola CPCAP PMIC battery driver"
>  	depends on MFD_CPCAP && IIO
> diff --git a/drivers/power/supply/Makefile b/drivers/power/supply/Makefile
> index e83aa843bcc6..04204174b047 100644
> --- a/drivers/power/supply/Makefile
> +++ b/drivers/power/supply/Makefile
> @@ -21,6 +21,7 @@ obj-$(CONFIG_BATTERY_88PM860X)	+= 88pm860x_battery.o
>  obj-$(CONFIG_BATTERY_ACT8945A)	+= act8945a_charger.o
>  obj-$(CONFIG_BATTERY_AXP20X)	+= axp20x_battery.o
>  obj-$(CONFIG_CHARGER_AXP20X)	+= axp20x_ac_power.o
> +obj-$(CONFIG_BATTERY_BMS)	+= qcom_bms.o
>  obj-$(CONFIG_BATTERY_CPCAP)	+= cpcap-battery.o
>  obj-$(CONFIG_BATTERY_DS2760)	+= ds2760_battery.o
>  obj-$(CONFIG_BATTERY_DS2780)	+= ds2780_battery.o
> diff --git a/drivers/power/supply/qcom_bms.c b/drivers/power/supply/qcom_bms.c
> new file mode 100644
> index 000000000000..718fd745c0f7
> --- /dev/null
> +++ b/drivers/power/supply/qcom_bms.c
> @@ -0,0 +1,487 @@
> +// SPDX-License-Identifier: GPL
> +
> +/*
> + * Qualcomm Battery Monitoring System driver
> + *
> + * Copyright (C) 2018 Craig Tatlor <ctatlor97@xxxxxxxxx>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/fixp-arith.h>
> +#include <linux/platform_device.h>
> +#include <linux/power_supply.h>
> +#include <linux/slab.h>
> +#include <linux/bitops.h>
> +#include <linux/of.h>
> +#include <linux/of_platform.h>
> +#include <linux/regmap.h>
> +#include <linux/irq.h>
> +#include <linux/interrupt.h>
> +#include <linux/iio/consumer.h>
> +
> +#define REG_BMS_OCV_FOR_SOC_DATA0	0x90
> +#define REG_BMS_SHDW_CC_DATA0		0xA8
> +#define REG_BMS_CC_DATA_CTL		0x42
> +#define REG_BMS_CC_CLEAR_CTL		0x4
> +
> +#define BMS_HOLD_OREG_DATA		BIT(0)
> +#define BMS_CLEAR_SHDW_CC		BIT(6)
> +
> +#define BMS_CC_READING_RESOLUTION_N	542535
> +#define BMS_CC_READING_RESOLUTION_D	10000
> +#define BMS_CC_READING_TICKS		56
> +#define BMS_SLEEP_CLK_HZ		32764
> +
> +#define SECONDS_PER_HOUR		3600
> +#define TEMPERATURE_COLS		5
> +#define MAX_CAPACITY_ROWS		50
> +
> +/* lookup table for ocv -> capacity conversion */
> +struct bms_ocv_lut {
> +	int rows;
> +	s8 temp_legend[TEMPERATURE_COLS];
> +	u8 capacity_legend[MAX_CAPACITY_ROWS];
> +	u32 lut[MAX_CAPACITY_ROWS][TEMPERATURE_COLS];
> +};
> +
> +/* lookup table for battery temperature -> fcc conversion */
> +struct bms_fcc_lut {
> +	s8 temp_legend[TEMPERATURE_COLS];
> +	u32 lut[TEMPERATURE_COLS];
> +};
> +
> +struct bms_device_info {
> +	struct device *dev;
> +	struct regmap *regmap;
> +	struct bms_ocv_lut ocv_lut;
> +	struct power_supply_desc bat_desc;
> +	struct bms_fcc_lut fcc_lut;
> +	struct iio_channel *adc;
> +	struct mutex bms_output_lock;
> +	u32 base_addr;
> +
> +	int ocv_thr_irq;
> +	u32 ocv;
> +};
> +
> +static bool between(int left, int right, int val)
> +{
> +	if (left <= val && val <= right)
> +		return true;
> +
> +	if (left >= val && val >= right)
> +		return true;
> +
> +	return false;
> +}
> +
> +static int interpolate_capacity(int temp, u32 ocv,
> +				struct bms_ocv_lut *ocv_lut)
> +{
> +	int pcj_minus_one = 0, pcj = 0, i2 = 0, i3 = 0, i, j;
> +
> +	for (j = 0; j < TEMPERATURE_COLS; j++)
> +		if (temp <= ocv_lut->temp_legend[j])
> +			break;
> +
> +	if (ocv >= ocv_lut->lut[0][j])
> +		return ocv_lut->capacity_legend[0];
> +
> +	if (ocv <= ocv_lut->lut[ocv_lut->rows-1][j-1])
> +		return ocv_lut->capacity_legend[ocv_lut->rows-1];
> +
> +	for (i = 0; i < ocv_lut->rows-1; i++) {
> +		if (between(ocv_lut->lut[i][j],
> +			    ocv_lut->lut[i+1][j], ocv))
> +			i2 = i;
> +
> +		if (between(ocv_lut->lut[i][j-1],
> +			    ocv_lut->lut[i+1][j-1], ocv))
> +			i3 = i;
> +	}
> +
> +	/* interpolate two capacities */
> +	pcj = fixp_linear_interpolate(ocv_lut->lut[i2][j],
> +				      ocv_lut->capacity_legend[i2],
> +				      ocv_lut->lut[i2+1][j],
> +				      ocv_lut->capacity_legend[i2+1],
> +				      ocv);
> +
> +	pcj_minus_one = fixp_linear_interpolate(ocv_lut->lut[i3][j-1],
> +						ocv_lut->capacity_legend[i3],
> +						ocv_lut->lut[i3+1][j-1],
> +						ocv_lut->capacity_legend[i3+1],
> +						ocv);
> +
> +	/* interpolate them with the battery temperature */
> +	return fixp_linear_interpolate(ocv_lut->temp_legend[j-1],
> +				       pcj_minus_one,
> +				       ocv_lut->temp_legend[j],
> +				       pcj,
> +				       temp);
> +}
> +
> +static int interpolate_fcc(int temp, struct bms_fcc_lut *fcc_lut)
> +{
> +	int i;
> +
> +	for (i = 0; i < TEMPERATURE_COLS; i++)
> +		if (temp <= fcc_lut->temp_legend[i])
> +			break;
> +
> +	return fixp_linear_interpolate(fcc_lut->temp_legend[i-1],
> +			     fcc_lut->lut[i-1],
> +			     fcc_lut->temp_legend[i],
> +			     fcc_lut->lut[i],
> +			     temp);
> +}
> +
> +static int bms_lock_output_data(struct bms_device_info *di)
> +{
> +	int ret;
> +
> +	ret = regmap_update_bits(di->regmap, di->base_addr +
> +				 REG_BMS_CC_DATA_CTL,
> +				 BMS_HOLD_OREG_DATA, BMS_HOLD_OREG_DATA);
> +	if (ret) {
> +		dev_err(di->dev, "failed to lock bms output: %d", ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * Sleep for at least 100 microseconds here to make sure
> +	 * there has been at least three cycles of the sleep clock
> +	 * so that the registers are correctly locked.
> +	 */
> +	usleep_range(100, 1000);
> +
> +	return 0;
> +}
> +
> +static int bms_unlock_output_data(struct bms_device_info *di)
> +{
> +	int ret;
> +
> +	ret = regmap_update_bits(di->regmap, di->base_addr +
> +				 REG_BMS_CC_DATA_CTL,
> +				 BMS_HOLD_OREG_DATA, 0);
> +	if (ret) {
> +		dev_err(di->dev, "failed to unlock bms output: %d", ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static int bms_read_ocv(struct bms_device_info *di, u32 *ocv)
> +{
> +	int ret;
> +	u16 read_ocv;
> +
> +	mutex_lock(&di->bms_output_lock);
> +
> +	ret = bms_lock_output_data(di);
> +	if (ret)
> +		goto err_lock;
> +
> +	ret = regmap_bulk_read(di->regmap, di->base_addr+
> +			       REG_BMS_OCV_FOR_SOC_DATA0, &read_ocv, 2);
> +	if (ret) {
> +		dev_err(di->dev, "open circuit voltage read failed: %d", ret);
> +		goto err_read;
> +	}
> +
> +	dev_dbg(di->dev, "read open circuit voltage of: %d mv", read_ocv);
> +
> +

one empty line is enough.

> +	*ocv = read_ocv * 1000;
> +
> +err_read:
> +	bms_unlock_output_data(di);
> +
> +err_lock:
> +	mutex_unlock(&di->bms_output_lock);
> +
> +	return ret;
> +}
> +
> +static int bms_read_cc(struct bms_device_info *di, s64 *cc_uah)
> +{
> +	int ret;
> +	s64 cc_raw_s36, cc_raw, cc_uv, cc_pvh;
> +
> +	mutex_lock(&di->bms_output_lock);
> +
> +	ret = bms_lock_output_data(di);
> +	if (ret)
> +		goto err_lock;
> +
> +	ret = regmap_bulk_read(di->regmap, di->base_addr +
> +			       REG_BMS_SHDW_CC_DATA0,
> +			       &cc_raw_s36, 5);
> +	if (ret) {
> +		dev_err(di->dev, "coulomb counter read failed: %d", ret);
> +		goto err_read;
> +	}
> +
> +	ret = bms_unlock_output_data(di);
> +	if (ret)
> +		goto err_lock;
> +
> +	mutex_unlock(&di->bms_output_lock);
> +
> +	cc_raw = sign_extend32(cc_raw_s36, 28);
> +
> +	/* convert raw to uv */
> +	cc_uv = div_s64(cc_raw * BMS_CC_READING_RESOLUTION_N,
> +			BMS_CC_READING_RESOLUTION_D);
> +
> +	/* convert uv to pvh */
> +	cc_pvh = div_s64(cc_uv * BMS_CC_READING_TICKS * 100000,
> +			 BMS_SLEEP_CLK_HZ * SECONDS_PER_HOUR);
> +
> +	/* divide by impedance */
> +	*cc_uah = div_s64(cc_pvh, 10000);
> +
> +	dev_dbg(di->dev, "read coulomb counter value of: %lld uah", *cc_uah);
> +
> +	return 0;
> +
> +err_read:
> +	bms_unlock_output_data(di);
> +
> +err_lock:
> +	mutex_unlock(&di->bms_output_lock);
> +
> +	return ret;
> +}
> +
> +static void bms_reset_cc(struct bms_device_info *di)
> +{
> +	int ret;
> +
> +	mutex_lock(&di->bms_output_lock);
> +
> +	ret = regmap_update_bits(di->regmap, di->base_addr +
> +				 REG_BMS_CC_CLEAR_CTL,
> +				 BMS_CLEAR_SHDW_CC,
> +				 BMS_CLEAR_SHDW_CC);
> +	if (ret) {
> +		dev_err(di->dev, "coulomb counter reset failed: %d", ret);
> +		goto err_lock;
> +	}
> +
> +	/* wait at least three sleep cycles for cc to reset */
> +	usleep_range(100, 1000);
> +
> +	ret = regmap_update_bits(di->regmap, di->base_addr +
> +				 REG_BMS_CC_CLEAR_CTL,
> +				 BMS_CLEAR_SHDW_CC, 0);
> +	if (ret)
> +		dev_err(di->dev, "coulomb counter re-enable failed: %d", ret);
> +
> +err_lock:
> +	mutex_unlock(&di->bms_output_lock);
> +}
> +
> +static int bms_calculate_capacity(struct bms_device_info *di, int *capacity)
> +{
> +	unsigned long fcc;
> +	int ret, temp, ocv_capacity, temp_degc;
> +	s64 cc = 0;
> +
> +	ret = iio_read_channel_raw(di->adc, &temp);
> +	if (ret < 0) {
> +		dev_err(di->dev, "failed to read temperature: %d", ret);
> +		return ret;
> +	}
> +
> +	temp_degc = DIV_ROUND_CLOSEST(temp, 1000);
> +
> +	ret = bms_read_cc(di, &cc);
> +	if (ret < 0) {
> +		dev_err(di->dev, "failed to read coulomb counter: %d", ret);
> +		return ret;
> +	}
> +
> +	/* interpolate capacity from open circuit voltage */
> +	ocv_capacity = interpolate_capacity(temp_degc, di->ocv,
> +					    &di->ocv_lut);
> +
> +	/* interpolate the full charge capacity from temperature */
> +	fcc = interpolate_fcc(temp_degc, &di->fcc_lut);
> +
> +	/* append coloumb counter to capacity */
> +	*capacity = DIV_ROUND_CLOSEST(fcc * ocv_capacity, 100);
> +	*capacity = div_s64((*capacity - cc) * 100, fcc);
> +
> +	return 0;
> +}
> +
> +
> +

one empty line is enough. 

> +/*
> + * Return power_supply property
> + */
> +static int bms_get_property(struct power_supply *psy,
> +				   enum power_supply_property psp,
> +				   union power_supply_propval *val)
> +{
> +	struct bms_device_info *di = power_supply_get_drvdata(psy);
> +	int ret;
> +
> +	switch (psp) {
> +	case POWER_SUPPLY_PROP_CAPACITY:
> +		ret = bms_calculate_capacity(di, &val->intval);
> +		break;
> +	default:
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +	if (val->intval == INT_MAX || val->intval == INT_MIN)
> +		ret = -EINVAL;
> +
> +	return ret;
> +}
> +
> +static enum power_supply_property bms_props[] = {
> +	POWER_SUPPLY_PROP_CAPACITY,
> +};

Why does the driver not expose the following battery information?

temperature info via POWER_SUPPLY_PROP_TEMP
ocv info via POWER_SUPPLY_PROP_VOLTAGE_OCV
CC info via POWER_SUPPLY_PROP_CHARGE_COUNTER
max current via POWER_SUPPLY_PROP_CURRENT_MAX

> +static irqreturn_t bms_ocv_thr_irq_handler(int irq, void *dev_id)
> +{
> +	struct bms_device_info *di = dev_id;
> +
> +	if (bms_read_ocv(di, &di->ocv) < 0)
> +		return IRQ_HANDLED;
> +
> +	bms_reset_cc(di);
> +	return IRQ_HANDLED;
> +}

You want to call power_supply_changed() here to notify userspace.

> +static int bms_probe(struct platform_device *pdev)
> +{
> +	struct power_supply_config psy_cfg = {};
> +	struct bms_device_info *di;
> +	struct power_supply *bat;
> +	int ret;
> +
> +	di = devm_kzalloc(&pdev->dev, sizeof(*di), GFP_KERNEL);
> +	if (!di)
> +		return -ENOMEM;
> +
> +	di->dev = &pdev->dev;
> +
> +	di->regmap = dev_get_regmap(pdev->dev.parent, NULL);
> +	if (!di->regmap) {
> +		dev_err(di->dev, "Unable to get regmap");
> +		return -EINVAL;
> +	}
> +
> +	di->adc = devm_iio_channel_get(&pdev->dev, "temp");
> +	if (IS_ERR(di->adc))
> +		return PTR_ERR(di->adc);
> +
> +	ret = of_property_read_u32(di->dev->of_node, "reg", &di->base_addr);
> +	if (ret < 0)
> +		return ret;
> +
> +	ret = of_property_read_u8_array(di->dev->of_node,
> +						 "qcom,ocv-temp-legend-celsius",
> +						 (u8 *)di->ocv_lut.temp_legend,
> +						 TEMPERATURE_COLS);
> +	if (ret < 0) {
> +		dev_err(di->dev, "no open circuit voltage temperature legend found");
> +		return ret;
> +	}
> +
> +	di->ocv_lut.rows = of_property_read_variable_u8_array(di->dev->of_node,
> +						 "qcom,ocv-capacity-legend",
> +						 di->ocv_lut.capacity_legend, 0,
> +						 MAX_CAPACITY_ROWS);
> +	if (di->ocv_lut.rows < 0) {
> +		dev_err(di->dev, "no open circuit voltage capacity legend found");
> +		return ret;
> +	}
> +
> +	ret = of_property_read_variable_u32_array(di->dev->of_node,
> +						  "qcom,ocv-lut-microvolt",
> +						  (u32 *)di->ocv_lut.lut,
> +						  TEMPERATURE_COLS,
> +						  TEMPERATURE_COLS *
> +						  MAX_CAPACITY_ROWS);
> +	if (ret < 0) {
> +		dev_err(di->dev, "no open circuit voltage lut array found");
> +		return ret;
> +	}
> +
> +	ret = of_property_read_u8_array(di->dev->of_node,
> +						 "qcom,fcc-temp-legend-celsius",
> +						 (u8 *)di->fcc_lut.temp_legend,
> +						 TEMPERATURE_COLS);
> +	if (ret < 0) {
> +		dev_err(di->dev, "no full charge capacity temperature legend found");
> +		return ret;
> +	}
> +
> +	ret = of_property_read_u32_array(di->dev->of_node,
> +						  "qcom,fcc-lut-microamp-hours",
> +						  di->fcc_lut.lut,
> +						  TEMPERATURE_COLS);
> +	if (ret < 0) {
> +		dev_err(di->dev, "no full charge capacity lut array found");
> +		return ret;
> +	}
> +
> +	ret = bms_read_ocv(di, &di->ocv);
> +	if (ret < 0) {
> +		dev_err(di->dev, "failed to read initial open circuit voltage: %d",
> +			ret);
> +		return ret;
> +	}
> +
> +	mutex_init(&di->bms_output_lock);
> +
> +	di->ocv_thr_irq = platform_get_irq_byname(pdev, "ocv_thr");
> +
> +	ret = devm_request_threaded_irq(di->dev, di->ocv_thr_irq, NULL,
> +					bms_ocv_thr_irq_handler,
> +					IRQF_TRIGGER_RISING | IRQF_ONESHOT,
> +					pdev->name, di);
> +	if (ret < 0) {
> +		dev_err(di->dev, "failed to request handler for open circuit voltage threshold IRQ");
> +		return ret;
> +	}
> +
> +

one empty line is enough.

> +	di->bat_desc.name = "bms";
> +	di->bat_desc.type = POWER_SUPPLY_TYPE_BATTERY;
> +	di->bat_desc.properties = bms_props;
> +	di->bat_desc.num_properties = ARRAY_SIZE(bms_props);
> +	di->bat_desc.get_property = bms_get_property;
> +
> +	psy_cfg.drv_data = di;

psy_cfg.of_node = pdev->dev.of_node;

> +	bat = devm_power_supply_register(di->dev, &di->bat_desc, &psy_cfg);
> +
> +	return PTR_ERR_OR_ZERO(bat);
> +}
> +
> +static const struct of_device_id bms_of_match[] = {
> +	{.compatible = "qcom,pm8941-bms", },
> +	{ },
> +};
> +MODULE_DEVICE_TABLE(of, bms_of_match);
> +
> +static struct platform_driver bms_driver = {
> +	.probe = bms_probe,
> +	.driver = {
> +		.name = "qcom-bms",
> +		.of_match_table = of_match_ptr(bms_of_match),
> +	},
> +};
> +module_platform_driver(bms_driver);
> +
> +MODULE_AUTHOR("Craig Tatlor <ctatlor97@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Qualcomm BMS driver");
> +MODULE_LICENSE("GPL");

Apart from the things above I would like to see the information
about the battery cell itself being moved to 'struct
power_supply_battery_info', see also my comment in the DT bindings.

-- Sebastian

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