Re: [PATCH v2 2/2] thermal/drivers/mediatek/lvts_thermal: Make reset optional for MT8196

[Philipp Zabel <p.zabel@pengutronix.de>]

On Di, 2026-07-21 at 12:52 +0200, AngeloGioacchino Del Regno wrote:
> Depending on the SoC+Firmware combination, the LVTS hardware may be
> may be actively used by one or even multiple concurrent MCUs!
> In this case, resetting it may produce either a severe slowdown of
> the entire system, or even a thermal protection AP reset, as some
> MCU(s) may be reading a very high or very low temperature while the
> LVTS is being reset.
> 
> On those, don't fail if no reset is found as that may be omitted on
> purpose, but still check if there's one, because some board(s) may
> be running on a different bootchain with reduced firmwares or using
> firmwares with reduced functionality.
> 
> So, use devm_reset_control_get_optional_exclusive() instead, as the
> LVTS controller always had only one reset and retrieving that by
> index, specifically, always made little sense anyway.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
> ---
>  drivers/thermal/mediatek/lvts_thermal.c | 15 ++++++++++++++-
>  1 file changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> index 92711896ce24..8b779fc5e970 100644
> --- a/drivers/thermal/mediatek/lvts_thermal.c
> +++ b/drivers/thermal/mediatek/lvts_thermal.c
> @@ -1473,7 +1473,20 @@ static int lvts_probe(struct platform_device *pdev)
>  	if (IS_ERR(lvts_td->base))
>  		return dev_err_probe(dev, PTR_ERR(lvts_td->base), "Failed to map io resource\n");
>  
> -	lvts_td->reset = devm_reset_control_get_by_index(dev, 0);
> +	/*
> +	 * Depending on the SoC+Firmware combination, the LVTS hardware may be
> +	 * may be actively used by one or even multiple concurrent MCUs!
> +	 * In this case, resetting it may produce either a severe slowdown of
> +	 * the entire system, or even a thermal protection AP reset, as some
> +	 * MCU(s) may be reading a very high or very low temperature while the
> +	 * LVTS is being reset.
> +	 *
> +	 * On those, don't fail if no reset is found as that may be omitted on
> +	 * purpose, but still check if there's one, because some board(s) may
> +	 * be running on a different bootchain with reduced firmwares or using
> +	 * firmwares with reduced functionality.
> +	 */
> +	lvts_td->reset = devm_reset_control_get_optional_exclusive(dev, NULL);

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

regards
Philipp