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Date:   Thu, 12 Apr 2018 21:08:57 -0700
From:   Eduardo Valentin <edubezval@gmail.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>,
        Zhang Rui <rui.zhang@intel.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc:     LKML <linux-kernel@vger.kernel.org>,
        Linux PM list <linux-pm@vger.kernel.org>,
        "Li, Philip" <philip.li@intel.com>
Subject: Re: [GIT PULL] Thermal management updates for v4.17-rc1
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Hello,

On Thu, Apr 12, 2018 at 09:55:19AM -0700, Linus Torvalds wrote:
> On Wed, Apr 11, 2018 at 10:08 PM, Zhang Rui <rui.zhang@intel.com> wrote:
> >
> > could you please illustrate me what the kconfig & warning is?
> 
> Just "make allmodconfig" and the warning is about a uninitialized variable.
> 
> Line 304 in drivers/thermal/samsung/exynos_tmu.c if my shell history
> is to be believed.
> 
>                 Linus

Yeah, this has also passed my local compilation error. Somehow my gcc4.9
is not catching it. Using an older gcc (gcc4.6) does catch it.

Anyways, given that the conversion functions are written to cover
for unexpected cal_type, the right way of fixing this is to rewrite
the conversion functions to allow for returning error codes and
adjusting the callers as expected.

Rui, bzolnier, please consider the following fix:

From 2aaf94f80c0021a21b4122c9f4197acff08ea398 Mon Sep 17 00:00:00 2001
From: Eduardo Valentin <edubezval@gmail.com>
Date: Thu, 12 Apr 2018 21:00:48 -0700
Subject: [PATCH 1/1] thermal: exynos: fix compilation warning around
 conversion functions

In order to fix the warns:
drivers/thermal/samsung/exynos_tmu.c:931:37: warning: 'temp' may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/thermal/samsung/exynos_tmu.c:304:9: warning: 'temp_code' may be used uninitialized in this function [-Wmaybe-uninitialized]

the conversion functions should allow return error codes
and the not mix the converted value with error code.

This patch change the conversion functions to return
error code or success and adjusts the callers accordingly.

Signed-off-by: Eduardo Valentin <edubezval@gmail.com>
---
 drivers/thermal/samsung/exynos_tmu.c | 120 ++++++++++++++++++++++++-----------
 1 file changed, 84 insertions(+), 36 deletions(-)

diff --git a/drivers/thermal/samsung/exynos_tmu.c b/drivers/thermal/samsung/exynos_tmu.c
index 2ec8548..b3f0704 100644
--- a/drivers/thermal/samsung/exynos_tmu.c
+++ b/drivers/thermal/samsung/exynos_tmu.c
@@ -282,52 +282,54 @@ static void exynos_report_trigger(struct exynos_tmu_data *p)
  * TMU treats temperature as a mapped temperature code.
  * The temperature is converted differently depending on the calibration type.
  */
-static int temp_to_code(struct exynos_tmu_data *data, u8 temp)
+static int temp_to_code(struct exynos_tmu_data *data, u8 temp, int *temp_code)
 {
-	int temp_code;
+	int ret = 0;
 
 	switch (data->cal_type) {
 	case TYPE_TWO_POINT_TRIMMING:
-		temp_code = (temp - EXYNOS_FIRST_POINT_TRIM) *
+		*temp_code = (temp - EXYNOS_FIRST_POINT_TRIM) *
 			(data->temp_error2 - data->temp_error1) /
 			(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) +
 			data->temp_error1;
 		break;
 	case TYPE_ONE_POINT_TRIMMING:
-		temp_code = temp + data->temp_error1 - EXYNOS_FIRST_POINT_TRIM;
+		*temp_code = temp + data->temp_error1 - EXYNOS_FIRST_POINT_TRIM;
 		break;
 	default:
 		WARN_ON(1);
+		ret = -EINVAL;
 		break;
 	}
 
-	return temp_code;
+	return ret;
 }
 
 /*
  * Calculate a temperature value from a temperature code.
  * The unit of the temperature is degree Celsius.
  */
-static int code_to_temp(struct exynos_tmu_data *data, u16 temp_code)
+static int code_to_temp(struct exynos_tmu_data *data, u16 temp_code, int *temp)
 {
-	int temp;
+	int ret = 0;
 
 	switch (data->cal_type) {
 	case TYPE_TWO_POINT_TRIMMING:
-		temp = (temp_code - data->temp_error1) *
+		*temp = (temp_code - data->temp_error1) *
 			(EXYNOS_SECOND_POINT_TRIM - EXYNOS_FIRST_POINT_TRIM) /
 			(data->temp_error2 - data->temp_error1) +
 			EXYNOS_FIRST_POINT_TRIM;
 		break;
 	case TYPE_ONE_POINT_TRIMMING:
-		temp = temp_code - data->temp_error1 + EXYNOS_FIRST_POINT_TRIM;
+		*temp = temp_code - data->temp_error1 + EXYNOS_FIRST_POINT_TRIM;
 		break;
 	default:
 		WARN_ON(1);
+		ret = -EINVAL;
 		break;
 	}
 
-	return temp;
+	return ret;
 }
 
 static void sanitize_temp_error(struct exynos_tmu_data *data, u32 trim_info)
@@ -352,7 +354,7 @@ static u32 get_th_reg(struct exynos_tmu_data *data, u32 threshold, bool falling)
 	struct thermal_zone_device *tz = data->tzd;
 	const struct thermal_trip * const trips =
 		of_thermal_get_trip_points(tz);
-	unsigned long temp;
+	int temp;
 	int i;
 
 	if (!trips) {
@@ -362,6 +364,8 @@ static u32 get_th_reg(struct exynos_tmu_data *data, u32 threshold, bool falling)
 	}
 
 	for (i = 0; i < of_thermal_get_ntrips(tz); i++) {
+		int val, ret;
+
 		if (trips[i].type == THERMAL_TRIP_CRITICAL)
 			continue;
 
@@ -371,7 +375,14 @@ static u32 get_th_reg(struct exynos_tmu_data *data, u32 threshold, bool falling)
 		else
 			threshold &= ~(0xff << 8 * i);
 
-		threshold |= temp_to_code(data, temp) << 8 * i;
+		ret = temp_to_code(data, temp, &val);
+		if (ret) {
+			pr_err("%s: Convertion error from temp (%d) to code: %d!\n",
+				__func__, temp, ret);
+			return 0;
+		}
+
+		threshold |= val << 8 * i;
 	}
 
 	return threshold;
@@ -460,11 +471,10 @@ static int exynos4210_tmu_initialize(struct platform_device *pdev)
 
 	/* Write temperature code for threshold */
 	reference = trips[0].temperature / MCELSIUS;
-	threshold_code = temp_to_code(data, reference);
-	if (threshold_code < 0) {
-		ret = threshold_code;
+	ret = temp_to_code(data, reference, &threshold_code);
+	if (ret < 0 || threshold_code < 0)
 		goto out;
-	}
+
 	writeb(threshold_code, data->base + EXYNOS4210_TMU_REG_THRESHOLD_TEMP);
 
 	for (i = 0; i < of_thermal_get_ntrips(tz); i++) {
@@ -537,7 +547,10 @@ static int exynos4412_tmu_initialize(struct platform_device *pdev)
 		goto out;
 	}
 
-	threshold_code = temp_to_code(data, crit_temp / MCELSIUS);
+	ret = temp_to_code(data, crit_temp / MCELSIUS, &threshold_code);
+	if (ret)
+		goto out;
+
 	/* 1-4 level to be assigned in th0 reg */
 	rising_threshold &= ~(0xff << 8 * i);
 	rising_threshold |= threshold_code << 8 * i;
@@ -620,7 +633,9 @@ static int exynos5433_tmu_initialize(struct platform_device *pdev)
 		/* Write temperature code for rising threshold */
 		tz->ops->get_trip_temp(tz, i, &temp);
 		temp /= MCELSIUS;
-		threshold_code = temp_to_code(data, temp);
+		ret = temp_to_code(data, temp, &threshold_code);
+		if (ret)
+			goto out;
 
 		rising_threshold = readl(data->base + rising_reg_offset);
 		rising_threshold |= (threshold_code << j * 8);
@@ -629,7 +644,9 @@ static int exynos5433_tmu_initialize(struct platform_device *pdev)
 		/* Write temperature code for falling threshold */
 		tz->ops->get_trip_hyst(tz, i, &temp_hist);
 		temp_hist = temp - (temp_hist / MCELSIUS);
-		threshold_code = temp_to_code(data, temp_hist);
+		ret = temp_to_code(data, temp_hist, &threshold_code);
+		if (ret)
+			goto out;
 
 		falling_threshold = readl(data->base + falling_reg_offset);
 		falling_threshold &= ~(0xff << j * 8);
@@ -677,7 +694,12 @@ static int exynos5440_tmu_initialize(struct platform_device *pdev)
 
 	/* if last threshold limit is also present */
 	if (!data->tzd->ops->get_crit_temp(data->tzd, &crit_temp)) {
-		threshold_code = temp_to_code(data, crit_temp / MCELSIUS);
+		int ret;
+
+		ret = temp_to_code(data, crit_temp / MCELSIUS, &threshold_code);
+		if (ret)
+			return ret;
+
 		/* 5th level to be assigned in th2 reg */
 		rising_threshold =
 			threshold_code << EXYNOS5440_TMU_TH_RISE4_SHIFT;
@@ -749,7 +771,10 @@ static int exynos7_tmu_initialize(struct platform_device *pdev)
 		temp_hist = temp - (temp_hist / MCELSIUS);
 
 		/* Set 9-bit temperature code for rising threshold levels */
-		threshold_code = temp_to_code(data, temp);
+		ret = temp_to_code(data, temp, &threshold_code);
+		if (ret)
+			goto out;
+
 		rising_threshold = readl(data->base +
 			EXYNOS7_THD_TEMP_RISE7_6 + reg_off);
 		rising_threshold &= ~(EXYNOS7_TMU_TEMP_MASK << (16 * bit_off));
@@ -758,7 +783,9 @@ static int exynos7_tmu_initialize(struct platform_device *pdev)
 		       data->base + EXYNOS7_THD_TEMP_RISE7_6 + reg_off);
 
 		/* Set 9-bit temperature code for falling threshold levels */
-		threshold_code = temp_to_code(data, temp_hist);
+		ret = temp_to_code(data, temp_hist, &threshold_code);
+		if (ret)
+			goto out;
 		falling_threshold &= ~(EXYNOS7_TMU_TEMP_MASK << (16 * bit_off));
 		falling_threshold |= threshold_code << (16 * bit_off);
 		writel(falling_threshold,
@@ -925,11 +952,18 @@ static int exynos_get_temp(void *p, int *temp)
 	clk_enable(data->clk);
 
 	value = data->tmu_read(data);
-	if (value < 0)
+	if (value < 0) {
 		ret = value;
-	else
-		*temp = code_to_temp(data, value) * MCELSIUS;
+		goto out;
+	}
+
+	ret = code_to_temp(data, value, temp);
+	if (ret)
+		goto out;
 
+	*temp *= MCELSIUS;
+
+out:
 	clk_disable(data->clk);
 	mutex_unlock(&data->lock);
 
@@ -937,9 +971,11 @@ static int exynos_get_temp(void *p, int *temp)
 }
 
 #ifdef CONFIG_THERMAL_EMULATION
-static u32 get_emul_con_reg(struct exynos_tmu_data *data, unsigned int val,
-			    int temp)
+static int get_emul_con_reg(struct exynos_tmu_data *data, unsigned int val,
+			    int temp, u32 *con_reg)
 {
+	int code, ret = 0;
+
 	if (temp) {
 		temp /= MCELSIUS;
 
@@ -950,27 +986,36 @@ static u32 get_emul_con_reg(struct exynos_tmu_data *data, unsigned int val,
 		if (data->soc == SOC_ARCH_EXYNOS7) {
 			val &= ~(EXYNOS7_EMUL_DATA_MASK <<
 				EXYNOS7_EMUL_DATA_SHIFT);
-			val |= (temp_to_code(data, temp) <<
-				EXYNOS7_EMUL_DATA_SHIFT) |
+			ret = temp_to_code(data, temp, &code);
+			if (ret)
+				goto out;
+
+			val |= (code << EXYNOS7_EMUL_DATA_SHIFT) |
 				EXYNOS_EMUL_ENABLE;
 		} else {
 			val &= ~(EXYNOS_EMUL_DATA_MASK <<
 				EXYNOS_EMUL_DATA_SHIFT);
-			val |= (temp_to_code(data, temp) <<
-				EXYNOS_EMUL_DATA_SHIFT) |
+			ret = temp_to_code(data, temp, &code);
+			if (ret)
+				goto out;
+
+			val |= (code << EXYNOS_EMUL_DATA_SHIFT) |
 				EXYNOS_EMUL_ENABLE;
 		}
 	} else {
 		val &= ~EXYNOS_EMUL_ENABLE;
 	}
 
-	return val;
+	*con_reg = val;
+out:
+	return ret;
 }
 
 static void exynos4412_tmu_set_emulation(struct exynos_tmu_data *data,
 					 int temp)
 {
 	unsigned int val;
+	int ret;
 	u32 emul_con;
 
 	if (data->soc == SOC_ARCH_EXYNOS5260)
@@ -983,18 +1028,21 @@ static void exynos4412_tmu_set_emulation(struct exynos_tmu_data *data,
 		emul_con = EXYNOS_EMUL_CON;
 
 	val = readl(data->base + emul_con);
-	val = get_emul_con_reg(data, val, temp);
-	writel(val, data->base + emul_con);
+	ret = get_emul_con_reg(data, val, temp, &val);
+	if (!ret)
+		writel(val, data->base + emul_con);
 }
 
 static void exynos5440_tmu_set_emulation(struct exynos_tmu_data *data,
 					 int temp)
 {
 	unsigned int val;
+	int ret;
 
 	val = readl(data->base + EXYNOS5440_TMU_S0_7_DEBUG);
-	val = get_emul_con_reg(data, val, temp);
-	writel(val, data->base + EXYNOS5440_TMU_S0_7_DEBUG);
+	ret = get_emul_con_reg(data, val, temp, &val);
+	if (!ret)
+		writel(val, data->base + EXYNOS5440_TMU_S0_7_DEBUG);
 }
 
 static int exynos_tmu_set_emulation(void *drv_data, int temp)
-- 
2.1.4