Hi,
On Tue, Jun 9, 2020 at 5:15 PM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@xxxxxxxxxxx> wrote:
>
> From: Dien Pham <dien.pham.ry@xxxxxxxxxxx>
>
> 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 name "reg" is not good because it should
> be the same type as rcar_gen3_thermal_read(). So, rename it with "ctemp".
>
> Signed-off-by: Van Do <van.do.xw@xxxxxxxxxxx>
> Signed-off-by: Dien Pham <dien.pham.ry@xxxxxxxxxxx>
> [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@xxxxxxxxxxx>
> ---
> Changes from v1:
> - Use int instead of long.
> - Rename "reg" with "ctemp".
> https://patchwork.kernel.org/patch/11593051/
>
> drivers/thermal/rcar_gen3_thermal.c | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/thermal/rcar_gen3_thermal.c b/drivers/thermal/rcar_gen3_thermal.c
> index 58fe7c1..49ea330 100644
> --- a/drivers/thermal/rcar_gen3_thermal.c
> +++ b/drivers/thermal/rcar_gen3_thermal.c
> @@ -167,16 +167,16 @@ static int rcar_gen3_thermal_get_temp(void *devdata, int *temp)
> {
> struct rcar_gen3_thermal_tsc *tsc = devdata;
> int mcelsius, val;
> - u32 reg;
> + int ctemp;
Wouldn't it be better to change the variable type to fix the bug in
this patch and make a separate one for the variable rename?
Regards,
Amit
> /* Read register and convert to mili Celsius */
> - reg = rcar_gen3_thermal_read(tsc, REG_GEN3_TEMP) & CTEMP_MASK;
> + ctemp = rcar_gen3_thermal_read(tsc, REG_GEN3_TEMP) & CTEMP_MASK;
>
> - if (reg <= thcode[tsc->id][1])
> - val = FIXPT_DIV(FIXPT_INT(reg) - tsc->coef.b1,
> + if (ctemp <= thcode[tsc->id][1])
> + val = FIXPT_DIV(FIXPT_INT(ctemp) - tsc->coef.b1,
> tsc->coef.a1);
> else
> - val = FIXPT_DIV(FIXPT_INT(reg) - tsc->coef.b2,
> + val = FIXPT_DIV(FIXPT_INT(ctemp) - tsc->coef.b2,
> tsc->coef.a2);
> mcelsius = FIXPT_TO_MCELSIUS(val);
>
> --
> 2.7.4
>
