Hi,
On Tue, Nov 23, 2021 at 12:41:40AM +0100, Linus Walleij wrote:
> Several batteries monitor the temperature of the battery using
> an NTC resistor. Add an NTC resistor resistance to temperature
> look-up table to struct power_supply_battery_info and use this
> in the AB8500 battery temperature driver to look up the battery
> temperature.
>
> Add a helper function in the power supply core:
> power_supply_ntc_resist2temp_simple(), which can use the
> NTC resistance table to look up and interpolate a temperature
> from the table.
>
> Fix up some of the confusing wording on the temperature to
> internal resistance table, and clarify what each resistance
> table is for.
>
> The AB8500 default NTC resistor is 47KOhm at 25 degrees
> Celsius and serves as a good example of how this usually works.
>
> Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> ---
This LGTM, but let's wait a bit to synchronize with the work
happening in the AXP driver.
-- Sebastian
> drivers/power/supply/ab8500-bm.h | 16 --------
> drivers/power/supply/ab8500_bmdata.c | 41 ++++++++++---------
> drivers/power/supply/ab8500_btemp.c | 45 ++------------------
> drivers/power/supply/power_supply_core.c | 52 ++++++++++++++++++++++++
> include/linux/power_supply.h | 34 ++++++++++++++++
> 5 files changed, 111 insertions(+), 77 deletions(-)
>
> diff --git a/drivers/power/supply/ab8500-bm.h b/drivers/power/supply/ab8500-bm.h
> index 57e1a8e27e51..90397f2a731f 100644
> --- a/drivers/power/supply/ab8500-bm.h
> +++ b/drivers/power/supply/ab8500-bm.h
> @@ -272,18 +272,6 @@ enum ab8500_adc_therm {
> AB8500_ADC_THERM_BATTEMP,
> };
>
> -/**
> - * struct ab8500_res_to_temp - defines one point in a temp to res curve. To
> - * be used in battery packs that combines the identification resistor with a
> - * NTC resistor.
> - * @temp: battery pack temperature in Celsius
> - * @resist: NTC resistor net total resistance
> - */
> -struct ab8500_res_to_temp {
> - int temp;
> - int resist;
> -};
> -
> /* Forward declaration */
> struct ab8500_fg;
>
> @@ -363,8 +351,6 @@ struct ab8500_maxim_parameters {
> * @maint_b_chg_timer_h: charge time in maintenance B state
> * @low_high_cur_lvl: charger current in temp low/high state in mA
> * @low_high_vol_lvl: charger voltage in temp low/high state in mV'
> - * @n_r_t_tbl_elements: number of elements in r_to_t_tbl
> - * @r_to_t_tbl: table containing resistance to temp points
> */
> struct ab8500_battery_type {
> int resis_high;
> @@ -377,8 +363,6 @@ struct ab8500_battery_type {
> int maint_b_chg_timer_h;
> int low_high_cur_lvl;
> int low_high_vol_lvl;
> - int n_temp_tbl_elements;
> - const struct ab8500_res_to_temp *r_to_t_tbl;
> };
>
> /**
> diff --git a/drivers/power/supply/ab8500_bmdata.c b/drivers/power/supply/ab8500_bmdata.c
> index 62953f9cb85a..aba459393ee6 100644
> --- a/drivers/power/supply/ab8500_bmdata.c
> +++ b/drivers/power/supply/ab8500_bmdata.c
> @@ -44,25 +44,25 @@ static struct power_supply_battery_ocv_table ocv_cap_tbl[] = {
> };
>
> /*
> - * Note that the res_to_temp table must be strictly sorted by falling
> + * Note that the ntc_res_to_temp_tbl table must be strictly sorted by falling
> * resistance values to work.
> */
> -static const struct ab8500_res_to_temp temp_tbl[] = {
> - {-5, 214834},
> - { 0, 162943},
> - { 5, 124820},
> - {10, 96520},
> - {15, 75306},
> - {20, 59254},
> - {25, 47000},
> - {30, 37566},
> - {35, 30245},
> - {40, 24520},
> - {45, 20010},
> - {50, 16432},
> - {55, 13576},
> - {60, 11280},
> - {65, 9425},
> +static struct power_supply_ntc_resistance_temp_table ntc_res_to_temp_tbl[] = {
> + { .resistance_ohm = 214834, .temp = -5},
> + { .resistance_ohm = 162943, .temp = 0},
> + { .resistance_ohm = 124820, .temp = 5},
> + { .resistance_ohm = 96520, .temp = 10},
> + { .resistance_ohm = 75306, .temp = 15},
> + { .resistance_ohm = 59254, .temp = 20},
> + { .resistance_ohm = 47000, .temp = 25},
> + { .resistance_ohm = 37566, .temp = 30},
> + { .resistance_ohm = 30245, .temp = 35},
> + { .resistance_ohm = 24520, .temp = 40},
> + { .resistance_ohm = 20010, .temp = 45},
> + { .resistance_ohm = 16432, .temp = 50},
> + { .resistance_ohm = 13576, .temp = 55},
> + { .resistance_ohm = 11280, .temp = 60},
> + { .resistance_ohm = 9425, .temp = 65},
> };
>
> /*
> @@ -92,8 +92,6 @@ static struct ab8500_battery_type bat_type_thermistor_unknown = {
> .maint_b_chg_timer_h = 200,
> .low_high_cur_lvl = 300,
> .low_high_vol_lvl = 4000,
> - .n_temp_tbl_elements = ARRAY_SIZE(temp_tbl),
> - .r_to_t_tbl = temp_tbl,
> };
>
> static const struct ab8500_bm_capacity_levels cap_levels = {
> @@ -217,6 +215,11 @@ int ab8500_bm_of_probe(struct power_supply *psy,
> bi->resist_table_size = ARRAY_SIZE(temp_to_batres_tbl_thermistor);
> }
>
> + if (!bi->ntc_resist_table) {
> + bi->ntc_resist_table = ntc_res_to_temp_tbl;
> + bi->ntc_resist_table_size = ARRAY_SIZE(ntc_res_to_temp_tbl);
> + }
> +
> if (!bi->ocv_table[0]) {
> /* Default capacity table at say 25 degrees Celsius */
> bi->ocv_temp[0] = 25;
> diff --git a/drivers/power/supply/ab8500_btemp.c b/drivers/power/supply/ab8500_btemp.c
> index 20253b8a7fe9..79528c18618d 100644
> --- a/drivers/power/supply/ab8500_btemp.c
> +++ b/drivers/power/supply/ab8500_btemp.c
> @@ -407,42 +407,6 @@ static int ab8500_btemp_get_batctrl_res(struct ab8500_btemp *di)
> return res;
> }
>
> -/**
> - * ab8500_btemp_res_to_temp() - resistance to temperature
> - * @di: pointer to the ab8500_btemp structure
> - * @tbl: pointer to the resiatance to temperature table
> - * @tbl_size: size of the resistance to temperature table
> - * @res: resistance to calculate the temperature from
> - *
> - * This function returns the battery temperature in degrees Celsius
> - * based on the NTC resistance.
> - */
> -static int ab8500_btemp_res_to_temp(struct ab8500_btemp *di,
> - const struct ab8500_res_to_temp *tbl, int tbl_size, int res)
> -{
> - int i;
> - /*
> - * Calculate the formula for the straight line
> - * Simple interpolation if we are within
> - * the resistance table limits, extrapolate
> - * if resistance is outside the limits.
> - */
> - if (res > tbl[0].resist)
> - i = 0;
> - else if (res <= tbl[tbl_size - 1].resist)
> - i = tbl_size - 2;
> - else {
> - i = 0;
> - while (!(res <= tbl[i].resist &&
> - res > tbl[i + 1].resist))
> - i++;
> - }
> -
> - return fixp_linear_interpolate(tbl[i].resist, tbl[i].temp,
> - tbl[i + 1].resist, tbl[i + 1].temp,
> - res);
> -}
> -
> /**
> * ab8500_btemp_measure_temp() - measure battery temperature
> * @di: pointer to the ab8500_btemp structure
> @@ -451,6 +415,7 @@ static int ab8500_btemp_res_to_temp(struct ab8500_btemp *di,
> */
> static int ab8500_btemp_measure_temp(struct ab8500_btemp *di)
> {
> + struct power_supply_battery_info *bi = &di->bm->bi;
> int temp, ret;
> static int prev;
> int rbat, rntc, vntc;
> @@ -469,9 +434,7 @@ static int ab8500_btemp_measure_temp(struct ab8500_btemp *di)
> return BTEMP_THERMAL_LOW_LIMIT;
> }
>
> - temp = ab8500_btemp_res_to_temp(di,
> - di->bm->bat_type->r_to_t_tbl,
> - di->bm->bat_type->n_temp_tbl_elements, rbat);
> + temp = power_supply_ntc_resist2temp_simple(bi, rbat);
> } else {
> ret = iio_read_channel_processed(di->btemp_ball, &vntc);
> if (ret < 0) {
> @@ -486,9 +449,7 @@ static int ab8500_btemp_measure_temp(struct ab8500_btemp *di)
> */
> rntc = 230000 * vntc / (VTVOUT_V - vntc);
>
> - temp = ab8500_btemp_res_to_temp(di,
> - di->bm->bat_type->r_to_t_tbl,
> - di->bm->bat_type->n_temp_tbl_elements, rntc);
> + temp = power_supply_ntc_resist2temp_simple(bi, rntc);
> prev = temp;
> }
> dev_dbg(di->dev, "Battery temperature is %d\n", temp);
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index 2723d7d0ced3..a870c3fe032c 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -589,6 +589,7 @@ int power_supply_get_battery_info(struct power_supply *psy,
> info->temp_max = INT_MAX;
> info->factory_internal_resistance_uohm = -EINVAL;
> info->resist_table = NULL;
> + info->ntc_resist_table = NULL;
>
> for (index = 0; index < POWER_SUPPLY_OCV_TEMP_MAX; index++) {
> info->ocv_table[index] = NULL;
> @@ -806,6 +807,57 @@ int power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *t
> }
> EXPORT_SYMBOL_GPL(power_supply_temp2resist_simple);
>
> +/**
> + * power_supply_ntc_resist2temp_simple() - find the battery temperature
> + * @info: battery information
> + * @resistance_ohm: Current NTC resistance value in microohm
> + *
> + * This helper function is used to look up battery internal temperature
> + * according to current NTC resistance value from one NTC resistance table.
> + * The NTC resistance table must be ordered descending by resistance:
> + * largest resistance with lowest temperature first, lowest resistance with
> + * highest temperature last. The function will interpolate to find the
> + * corresponding temperature.
> + *
> + * Return: the battery temperature.
> + */
> +int power_supply_ntc_resist2temp_simple(struct power_supply_battery_info *info,
> + int resistance_ohm)
> +{
> + struct power_supply_ntc_resistance_temp_table *table;
> + int i, high, low;
> + int table_len;
> +
> + table = info->ntc_resist_table;
> + table_len = info->ntc_resist_table_size;
> +
> + if (!table || !table_len) {
> + pr_err("Empty battery NTC resistance table, assume 25 degrees\n");
> + return 25;
> + }
> + if (!resistance_ohm)
> + pr_info("Battery NTC resistance 0, this is unlikely\n");
> +
> + /* Break loop at table_len - 1 because that is the highest index */
> + for (i = 0; i < table_len - 1; i++)
> + if (resistance_ohm > table[i].resistance_ohm)
> + break;
> +
> + /* The library function will deal with high == low */
> + if ((i == 0) || (i == (table_len - 1)))
> + high = i;
> + else
> + high = i - 1;
> + low = i;
> +
> + return fixp_linear_interpolate(table[low].resistance_ohm,
> + table[low].temp,
> + table[high].resistance_ohm,
> + table[high].temp,
> + resistance_ohm);
> +}
> +EXPORT_SYMBOL_GPL(power_supply_ntc_resist2temp_simple);
> +
> /**
> * power_supply_ocv2cap_simple() - find the battery capacity
> * @table: Pointer to battery OCV lookup table
> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
> index b5079109ac00..a0da806185b5 100644
> --- a/include/linux/power_supply.h
> +++ b/include/linux/power_supply.h
> @@ -335,11 +335,29 @@ struct power_supply_battery_ocv_table {
> int capacity; /* percent */
> };
>
> +/**
> + * struct power_supply_resistance_temp_table - correlate temperature to resistance
> + * @temp: the internal temperature of the battery in degrees Celsius
> + * @resistance: the percentage of the factory internal resistance at this
> + * temperature, usually nomimal factory resistance is 100 percent at 25
> + * degrees Celsius, lower at higher temperature and higher at lower
> + * temperature.
> + */
> struct power_supply_resistance_temp_table {
> int temp; /* celsius */
> int resistance; /* internal resistance percent */
> };
>
> +/**
> + * struct power_supply_ntc_resistance_temp_table - correlate NTC to temp
> + * @resistance: the NTC resistance in ohm
> + * @temp: the corresponding temperature in degrees Celsius
> + */
> +struct power_supply_ntc_resistance_temp_table {
> + int resistance_ohm;
> + int temp;
> +};
> +
> #define POWER_SUPPLY_OCV_TEMP_MAX 20
>
> /**
> @@ -426,6 +444,18 @@ struct power_supply_resistance_temp_table {
> * by temperature: highest temperature with lowest resistance first, lowest
> * temperature with highest resistance last.
> * @resist_table_size: the number of items in the resist_table.
> + * @ntc_resist_table: this is a table that correlates a resistance of a negative
> + * temperature coefficient (NTC) resistor to an internal temperature of a
> + * battery. This can be achieved by a separate thermistor to
> + * supply voltage on a third terminal on a battery which is the most
> + * reliable. An external thermistor can also be used sometimes. Knowing the
> + * temperature of the battery is usually necessary to perform a lookup in the
> + * resist_table to determine the internal resistance of the battery, and
> + * to find the right ocv_table to determine the capacity of the battery.
> + * The NTC resistance table must be ordered descending by resistance:
> + * largest resistance with lowest temperature first, lowest resistance with
> + * highest temperature last.
> + * @ntc_resist_table_size: the number of items in the ntc_resist_table.
> *
> * This is the recommended struct to manage static battery parameters,
> * populated by power_supply_get_battery_info(). Most platform drivers should
> @@ -546,6 +576,8 @@ struct power_supply_battery_info {
> int ocv_table_size[POWER_SUPPLY_OCV_TEMP_MAX];
> struct power_supply_resistance_temp_table *resist_table;
> int resist_table_size;
> + struct power_supply_ntc_resistance_temp_table *ntc_resist_table;
> + int ntc_resist_table_size;
> };
>
> extern struct atomic_notifier_head power_supply_notifier;
> @@ -587,6 +619,8 @@ extern int power_supply_batinfo_ocv2cap(struct power_supply_battery_info *info,
> extern int
> power_supply_temp2resist_simple(struct power_supply_resistance_temp_table *table,
> int table_len, int temp);
> +extern int power_supply_ntc_resist2temp_simple(struct power_supply_battery_info *info,
> + int resistance_ohm);
> extern void power_supply_changed(struct power_supply *psy);
> extern int power_supply_am_i_supplied(struct power_supply *psy);
> extern int power_supply_set_input_current_limit_from_supplier(
> --
> 2.31.1
>
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