linux-kernel - Re: [PATCH RESEND v3 3/9] thermal/drivers/mediatek/lvts: Guard against zero temp_factor in lvts_raw_to

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Message-ID: <84b9fd00-ce75-43bf-a53b-48818628f7e2@linaro.org>
Date: Mon, 10 Nov 2025 13:42:06 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Laura Nao <laura.nao@...labora.com>, srini@...nel.org, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, rafael@...nel.org,
 rui.zhang@...el.com, lukasz.luba@....com, matthias.bgg@...il.com,
 angelogioacchino.delregno@...labora.com
Cc: nfraprado@...labora.com, arnd@...db.de, colin.i.king@...il.com,
 u.kleine-koenig@...libre.com, andrew-ct.chen@...iatek.com,
 lala.lin@...iatek.com, bchihi@...libre.com, frank-w@...lic-files.de,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org, kernel@...labora.com,
 Chen-Yu Tsai <wenst@...omium.org>, Fei Shao <fshao@...omium.org>
Subject: Re: [PATCH RESEND v3 3/9] thermal/drivers/mediatek/lvts: Guard
 against zero temp_factor in lvts_raw_to_temp

On 10/16/25 16:21, Laura Nao wrote:
> Add a guard against zero temp_factor in lvts_raw_to_temp() to prevent
> division by zero and ensure safe conversion.

Is the temp_factor something else than a ro data statically initialized 
by the lvts_data structure ?

It is pointless to handle the case where the temp_factor is zero. If we 
read the temperature the kernel crashes immediately (which means it was 
not tested).

The temp_factor is an internal value of the driver. If the temp_factor 
is zero, the driver is buggy and should be fixed.


> Fixes: 6725a29321e4 ("thermal/drivers/mediatek/lvts_thermal: Make coeff configurable")
> Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>
> Reviewed-by: Fei Shao <fshao@...omium.org>
> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Tested-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> Signed-off-by: Laura Nao <laura.nao@...labora.com>
> ---
>   drivers/thermal/mediatek/lvts_thermal.c | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> index 1c54d0b75b1a..4ef549386add 100644
> --- a/drivers/thermal/mediatek/lvts_thermal.c
> +++ b/drivers/thermal/mediatek/lvts_thermal.c
> @@ -284,11 +284,14 @@ 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)
> @@ -1346,6 +1349,9 @@ static int lvts_probe(struct platform_device *pdev)
>   	if (irq < 0)
>   		return irq;
>   
> +	if (!lvts_data->temp_factor)
> +		dev_warn(dev, "temp_factor should never be zero; check platform data.\n");
> +
>   	golden_temp_offset = lvts_data->temp_offset;
>   
>   	ret = lvts_domain_init(dev, lvts_td, lvts_data);
If





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