[v3] thermal: rcar_gen3_thermal: Fix undefined temperature if negative

Message ID 1593053768-31016-1-git-send-email-yoshihiro.shimoda.uh@renesas.com
State New
Headers show
  • [v3] thermal: rcar_gen3_thermal: Fix undefined temperature if negative
Related show

Commit Message

Yoshihiro Shimoda June 25, 2020, 2:56 a.m.
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, there is better to rename it in a further patch as

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>
 Changes from v2:
 - Add Niklas-san's Reviewed-by and Tested-by.
 - Keep the variable name "reg" and revise the commit description for it.

 Changes from v1:
 - Use int instead of long.
 - Rename "reg" with "ctemp".

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


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;