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>

1 files changed, 22 insertions, 81 deletions

diff --git a/drivers/power/supply/ab8500_btemp.c b/drivers/power/supply/ab8500_btemp.c
index a5ca09124c93..2a6fc151210c 100644
--- a/drivers/power/supply/ab8500_btemp.c
+++ b/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;
@@ -229,76 +228,6 @@ static int ab8500_btemp_get_batctrl_res(struct ab8500_btemp *di)
 }
 
 /**
- * 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 */
-	di->btemp_ball = devm_iio_channel_get(dev, "btemp_ball");
-	if (IS_ERR(di->btemp_ball)) {
-		ret = dev_err_probe(dev, PTR_ERR(di->btemp_ball),
-				    "failed to get BTEMP BALL ADC channel\n");
-		return ret;
+	/* Get thermal zone and ADC */
+	di->tz = thermal_zone_get_zone_by_name("battery-thermal");
+	if (IS_ERR(di->tz)) {
+		return dev_err_probe(dev, PTR_ERR(di->tz),
+				     "failed to get battery thermal zone\n");
 	}
 	di->bat_ctrl = devm_iio_channel_get(dev, "bat_ctrl");
 	if (IS_ERR(di->bat_ctrl)) {