power: supply: ab8500: Integrate thermal zone

Instead of providing our own homebrewn thermal measurement
code for an NTC and passing tables, we put the NTC thermistor
into the device tree, create a passive thermal zone, and poll
this thermal zone for the temperature.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/Kconfig

@@ -728,6 +728,8 @@ config BATTERY_GAUGE_LTC2941
 config AB8500_BM
 	bool "AB8500 Battery Management Driver"
 	depends on AB8500_CORE && AB8500_GPADC && (IIO = y) && OF
+	select THERMAL
+	select THERMAL_OF
 	help
 	  Say Y to include support for AB8500 battery management.
 

drivers/power/supply/ab8500-bm.h

@@ -260,18 +260,6 @@ enum bup_vch_sel {
 #define BUS_PP_PRECHG_CURRENT_MASK		0x0E
 #define BUS_POWER_PATH_PRECHG_ENA		0x01
 
-/**
- * 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;
 
@@ -351,8 +339,6 @@ 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;
@@ -365,8 +351,6 @@ 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;
 };
 
 /**
@@ -449,23 +433,6 @@ struct ab8500_bm_data {
 	const struct ab8500_fg_parameters *fg_params;
 };
 
-enum {
-	NTC_EXTERNAL = 0,
-	NTC_INTERNAL,
-};
-
-/**
- * struct 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 res_to_temp {
-	int temp;
-	int resist;
-};
-
 /* Forward declaration */
 struct ab8500_fg;
 

drivers/power/supply/ab8500_bmdata.c

@@ -43,28 +43,6 @@ static struct power_supply_battery_ocv_table ocv_cap_tbl[] = {
 	{ .ocv = 3094000, .capacity = 0},
 };
 
-/*
- * Note that the res_to_temp 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},
-};
-
 /*
  * Note that the batres_vs_temp table must be strictly sorted by falling
  * temperature values to work. Factory resistance is 300 mOhm and the
@@ -92,8 +70,6 @@ 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 = {

drivers/power/supply/ab8500_btemp.c

@@ -26,13 +26,12 @@
 #include <linux/mfd/core.h>
 #include <linux/mfd/abx500.h>
 #include <linux/mfd/abx500/ab8500.h>
+#include <linux/thermal.h>
 #include <linux/iio/consumer.h>
 #include <linux/fixp-arith.h>
 
 #include "ab8500-bm.h"
 
-#define VTVOUT_V			1800
-
 #define BTEMP_THERMAL_LOW_LIMIT		-10
 #define BTEMP_THERMAL_MED_LIMIT		0
 #define BTEMP_THERMAL_HIGH_LIMIT_52	52
@@ -82,7 +81,7 @@ struct ab8500_btemp_ranges {
  * @bat_temp:		Dispatched battery temperature in degree Celsius
  * @prev_bat_temp	Last measured battery temperature in degree Celsius
  * @parent:		Pointer to the struct ab8500
- * @adc_btemp_ball:	ADC channel for the battery ball temperature
+ * @tz:			Thermal zone for the battery
  * @adc_bat_ctrl:	ADC channel for the battery control
  * @fg:			Pointer to the struct fg
  * @bm:           	Platform specific battery management information
@@ -100,7 +99,7 @@ struct ab8500_btemp {
 	int bat_temp;
 	int prev_bat_temp;
 	struct ab8500 *parent;
-	struct iio_channel *btemp_ball;
+	struct thermal_zone_device *tz;
 	struct iio_channel *bat_ctrl;
 	struct ab8500_fg *fg;
 	struct ab8500_bm_data *bm;
@@ -228,76 +227,6 @@ 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
- *
- * Returns battery temperature (on success) else the previous temperature
- */
-static int ab8500_btemp_measure_temp(struct ab8500_btemp *di)
-{
-	int temp, ret;
-	static int prev;
-	int rntc, vntc;
-
-	ret = iio_read_channel_processed(di->btemp_ball, &vntc);
-	if (ret < 0) {
-		dev_err(di->dev,
-			"%s ADC conversion failed,"
-			" using previous value\n", __func__);
-		return prev;
-	}
-	/*
-	 * The PCB NTC is sourced from VTVOUT via a 230kOhm
-	 * resistor.
-	 */
-	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);
-	prev = temp;
-
-	dev_dbg(di->dev, "Battery temperature is %d\n", temp);
-	return temp;
-}
-
 /**
  * ab8500_btemp_id() - Identify the connected battery
  * @di:		pointer to the ab8500_btemp structure
@@ -347,6 +276,9 @@ static void ab8500_btemp_periodic_work(struct work_struct *work)
 	int bat_temp;
 	struct ab8500_btemp *di = container_of(work,
 		struct ab8500_btemp, btemp_periodic_work.work);
+	/* Assume 25 degrees celsius as start temperature */
+	static int prev = 25;
+	int ret;
 
 	if (!di->initialized) {
 		/* Identify the battery */
@@ -354,7 +286,17 @@ static void ab8500_btemp_periodic_work(struct work_struct *work)
 			dev_warn(di->dev, "failed to identify the battery\n");
 	}
 
-	bat_temp = ab8500_btemp_measure_temp(di);
+	/* Failover if a reading is erroneous, use last meausurement */
+	ret = thermal_zone_get_temp(di->tz, &bat_temp);
+	if (ret) {
+		dev_err(di->dev, "error reading temperature\n");
+		bat_temp = prev;
+	} else {
+		/* Convert from millicentigrades to centigrades */
+		bat_temp /= 1000;
+		prev = bat_temp;
+	}
+
 	/*
 	 * Filter battery temperature.
 	 * Allow direct updates on temperature only if two samples result in
@@ -783,12 +725,11 @@ static int ab8500_btemp_probe(struct platform_device *pdev)
 	di->dev = dev;
 	di->parent = dev_get_drvdata(pdev->dev.parent);
 
-	/* Get ADC channels */
+	/* Get thermal zone and ADC */
-	di->btemp_ball = devm_iio_channel_get(dev, "btemp_ball");
+	di->tz = thermal_zone_get_zone_by_name("battery-thermal");
-	if (IS_ERR(di->btemp_ball)) {
+	if (IS_ERR(di->tz)) {
-		ret = dev_err_probe(dev, PTR_ERR(di->btemp_ball),
+		return dev_err_probe(dev, PTR_ERR(di->tz),
-				    "failed to get BTEMP BALL ADC channel\n");
+				     "failed to get battery thermal zone\n");
-		return ret;
 	}
 	di->bat_ctrl = devm_iio_channel_get(dev, "bat_ctrl");
 	if (IS_ERR(di->bat_ctrl)) {