[v4] thermal: rcar_gen3_thermal: Fix undefined temperature if negative
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Message ID 1593085099-2057-1-git-send-email-yoshihiro.shimoda.uh@renesas.com
State New
Delegated to: Daniel Lezcano
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Series
  • [v4] thermal: rcar_gen3_thermal: Fix undefined temperature if negative
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Commit Message

Yoshihiro Shimoda June 25, 2020, 11:38 a.m. UTC
From: Dien Pham <dien.pham.ry@renesas.com>

As description for DIV_ROUND_CLOSEST in file include/linux/kernel.h.
  "Result is undefined for negative divisors if the dividend variable
   type is unsigned and for negative dividends if the divisor variable
   type is unsigned."

In current code, the FIXPT_DIV uses DIV_ROUND_CLOSEST but has not
checked sign of divisor before using. It makes undefined temperature
value in case the value is negative.

This patch fixes to satisfy DIV_ROUND_CLOSEST description
and fix bug too. Note that the variable name "reg" is not good
because it should be the same type as rcar_gen3_thermal_read().
However, it's better to rename the "reg" in a further patch as
cleanup.

Signed-off-by: Van Do <van.do.xw@renesas.com>
Signed-off-by: Dien Pham <dien.pham.ry@renesas.com>
[shimoda: minor fixes, add Fixes tag]
Fixes: 564e73d283af ("thermal: rcar_gen3_thermal: Add R-Car Gen3 thermal driver")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Niklas Soderlund <niklas.soderlund+renesas@ragnatech.se>
Tested-by: Niklas Soderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Amit Kucheria <amit.kucheria@linaro.org>
---
 Changes from v3:
 - Add Amit's Reviewed-by.
 - Fix typos in the commit description.
 https://patchwork.kernel.org/patch/11624619/

 Changes from v2:
 - Add Niklas-san's Reviewed-by and Tested-by.
 - Keep the variable name "reg" and revise the commit description for it.
 https://patchwork.kernel.org/patch/11595327/

 Changes from v1:
 - Use int instead of long.
 - Rename "reg" with "ctemp".
 https://patchwork.kernel.org/patch/11593051/

 drivers/thermal/rcar_gen3_thermal.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch
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diff --git a/drivers/thermal/rcar_gen3_thermal.c b/drivers/thermal/rcar_gen3_thermal.c
index 58fe7c1..c48c5e9 100644
--- a/drivers/thermal/rcar_gen3_thermal.c
+++ b/drivers/thermal/rcar_gen3_thermal.c
@@ -167,7 +167,7 @@  static int rcar_gen3_thermal_get_temp(void *devdata, int *temp)
 {
 	struct rcar_gen3_thermal_tsc *tsc = devdata;
 	int mcelsius, val;
-	u32 reg;
+	int reg;
 
 	/* Read register and convert to mili Celsius */
 	reg = rcar_gen3_thermal_read(tsc, REG_GEN3_TEMP) & CTEMP_MASK;