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: <20250722095752.28245-1-laura.nao@collabora.com>
Date: Tue, 22 Jul 2025 11:57:52 +0200
From: Laura Nao <laura.nao@...labora.com>
To: wenst@...omium.org
Cc: andrew-ct.chen@...iatek.com,
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Subject: Re: [PATCH 3/9] thermal/drivers/mediatek/lvts: Guard against zero temp_factor in lvts_raw_to_temp

On 7/21/25 12:08, Chen-Yu Tsai wrote:
> 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?
>

Yes, this should only occur with incorrect platform data. Adding a
warning in the probe function sounds like a good idea to catch 
any misconfiguration early. I’ll include that in the next revision.

Thanks,

Laura

> 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
>>
>>