Re: [PATCH v1 2/2] drm/panthor: treat sram as mandatory except mt8196

[Boris Brezillon]

On Sun, 15 Feb 2026 13:02:51 +0300
Onur Özkan <work@xxxxxxxxxxxxx> wrote:

> If sram-supply is missing, Panthor falls back to a
> dummy regulator with a warning. This implicit behavior
> hides missing DT wiring behind regulator core fallback.
> 
> Make SRAM handling explicit: require sram-supply for all
> Panthor compatibles except mt8196-mali where GPU supplies
> are intentionally managed outside Panthor and DT does not
> model sram-supply for that compatible.
> 
> This keeps DT power modeling explicit and avoids relying on
> dummy-regulator fallback.
> 
> Link: https://lore.kernel.org/all/20260213155937.6af75786@nimda/
> Signed-off-by: Onur Özkan <work@xxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/panthor/panthor_devfreq.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panthor/panthor_devfreq.c b/drivers/gpu/drm/panthor/panthor_devfreq.c
> index 2249b41ca4af..5f6075f18fe3 100644
> --- a/drivers/gpu/drm/panthor/panthor_devfreq.c
> +++ b/drivers/gpu/drm/panthor/panthor_devfreq.c
> @@ -206,12 +206,17 @@ int panthor_devfreq_init(struct panthor_device *ptdev)
>  	 * But without knowing if it's beneficial or not (in term of power
>  	 * consumption), or how much it slows down the suspend/resume steps,
>  	 * let's just keep regulators enabled for the device lifetime.
> +	 *
> +	 * Treat sram-supply as mandatory except for mt8196-mali. It manages
> +	 * SRAM outside Panthor so this driver must not require direct control
> +	 * over it.
>  	 */
> -	ret = devm_regulator_get_enable_optional(dev, "sram");
> -	if (ret && ret != -ENODEV) {
> -		if (ret != -EPROBE_DEFER)
> +	if (!of_device_is_compatible(dev->of_node, "mediatek,mt8196-mali")) {

Rather than checking for specific compats here, let's go for
a dont_need_sram_supply bool in panthor_soc_data.

> +		ret = devm_regulator_get_enable_optional(dev, "sram");

If we assume SRAM supply is mandatory, should this be
devm_regulator_get_enable() instead?

> +		if (ret) {
>  			DRM_DEV_ERROR(dev, "Couldn't retrieve/enable sram supply\n");
> -		return ret;
> +			return ret;
> +		}
>  	}
>  
>  	opp = devfreq_recommended_opp(dev, &cur_freq, 0);