linux-kernel - Re: [PATCH 3/9] thermal/drivers/mediatek/lvts: Guard against zero temp_factor in lvts_raw_to

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Message-ID: <CAGXv+5F51DiCHi_QPeDKOGCwvgM6HpmRjEjSgS8-mh=Fg1Fr5g@mail.gmail.com>
Date: Mon, 21 Jul 2025 18:08:08 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Laura Nao <laura.nao@...labora.com>
Cc: srini@...nel.org, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	rafael@...nel.org, daniel.lezcano@...aro.org, rui.zhang@...el.com, 
	lukasz.luba@....com, matthias.bgg@...il.com, 
	angelogioacchino.delregno@...labora.com, andrew-ct.chen@...iatek.com, 
	lala.lin@...iatek.com, arnd@...db.de, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, nfraprado@...labora.com, 
	devicetree@...r.kernel.org, u.kleine-koenig@...libre.com, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	kernel@...labora.com, colin.i.king@...il.com, bchihi@...libre.com
Subject: Re: [PATCH 3/9] thermal/drivers/mediatek/lvts: Guard against zero
 temp_factor in lvts_raw_to_temp

On Mon, Jul 21, 2025 at 4:26 PM Laura Nao <laura.nao@...labora.com> wrote:
>
> Add a guard against zero temp_factor in lvts_raw_to_temp() to prevent
> division by zero and ensure safe conversion.
>
> Fixes: 6725a29321e4 ("thermal/drivers/mediatek/lvts_thermal: Make coeff configurable")
> Signed-off-by: Laura Nao <laura.nao@...labora.com>

Code wise,

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

However I assume this would only happen with bad platform data? The
factor should _never_ be zero. Maybe also issue a warning in the probe
function?

ChenYu

> ---
>  drivers/thermal/mediatek/lvts_thermal.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> index 8d5259b9d03b..b80c2929ae74 100644
> --- a/drivers/thermal/mediatek/lvts_thermal.c
> +++ b/drivers/thermal/mediatek/lvts_thermal.c
> @@ -280,11 +280,14 @@ static int lvts_raw_to_temp(u32 raw_temp, int temp_factor)
>
>  static u32 lvts_temp_to_raw(int temperature, int temp_factor)
>  {
> -       u32 raw_temp = ((s64)(golden_temp_offset - temperature)) << 14;
> +       u32 raw_temp;
>
> -       raw_temp = div_s64(raw_temp, -temp_factor);
> +       if (temp_factor == 0)
> +               return temperature;
>
> -       return raw_temp;
> +       raw_temp = ((s64)(golden_temp_offset - temperature)) << 14;
> +
> +       return div_s64(raw_temp, -temp_factor);
>  }
>
>  static int lvts_get_temp(struct thermal_zone_device *tz, int *temp)
> --
> 2.39.5
>
>