Re: Re: [PATCH 1/2] dt-bindings: gpu: mali-valhall-csf: Document i.MX952 support

[Liviu Dudau]

On Wed, Apr 01, 2026 at 09:43:12AM +0000, Guangliu Ding wrote:
> Hi Daniel
> 
> > On 4/1/26 11:48, Guangliu Ding wrote:
> > > [You don't often get email from guangliu.ding@xxxxxxx. Learn why this
> > > is important at https://aka.ms/LearnAboutSenderIdentification ]
> > >
> > > Hi Liviu
> > >
> > > Thanks for your review. Please refer to my comments below:
> > >
> > >> On Tue, Mar 31, 2026 at 06:12:38PM +0800, Guangliu Ding wrote:
> > >>> Add compatible string of Mali G310 GPU on i.MX952 board.
> > >>>
> > >>> Signed-off-by: Guangliu Ding <guangliu.ding@xxxxxxx>
> > >>> Reviewed-by: Jiyu Yang <jiyu.yang@xxxxxxx>
> > >>> ---
> > >>>  Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml | 1
> > >>> +
> > >>>  1 file changed, 1 insertion(+)
> > >>>
> > >>> diff --git
> > >>> a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> > >> b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> > >>> index 8eccd4338a2b..6a10843a26e2 100644
> > >>> ---
> > >>> a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
> > >>> +++ b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yam
> > >>> +++ l
> > >>> @@ -20,6 +20,7 @@ properties:
> > >>>            - enum:
> > >>>                - mediatek,mt8196-mali
> > >>>                - nxp,imx95-mali            # G310
> > >>> +              - nxp,imx952-mali           # G310
> > >> Can you explain why this is needed? Can it not be covered by the
> > >> existing compatible?
> > > There are functional differences in GPU module (GPUMIX) between i.MX95
> > > and i.MX952. So they cannot be fully covered by a single existing compatible.
> > > On i.MX952, The GPU clock is controlled by hardware GPU auto
> > > clock-gating mechanism, while the GPU clock is managed explicitly by the
> > driver on i.MX95.
> > > Because of these behavioral differences, separate compatible strings
> > > "nxp,imx95-mali" and "nxp,imx952-mali" are needed to allow the driver
> > > to handle the two variants independently and to keep room for future
> > divergence.
> > 
> > 
> > This information should be added in the commit message explaining why
> > 
> > the change is needed.
> > 
> > 
> > But then where is the driver code taking care of these diferences?
> > 
> 
> Yes. Currently the driver does not require "nxp,imx952-mali" string.
> However, when GPU ipa_counters are enabled to calculate the GPU busy_time/idle_time for 
> GPU DVFS feature, they will conflict with the hardware GPU auto clock‑gating mechanism, 
> causing GPU clock to remain always on.
> In such cases, ipa_counters need to be disabled so that the GPU auto clock‑gating 
> mechanism can operate normally, using "nxp,imx952-mali" string.

OK, I understand that you're following guidance from some other senior people on how
to upstream patches so you've tried to create the smallest patchset to ensure that
it gets reviewed and accepted, but in this case we need to see the other patches as well
to decide if your approach is the right one and we do need a separate compatible string.

If enabling GPU ipa_counters causes the clocks to get stuck active, that feels like a
hardware bug, so figuring out how to handle that is more important than adding a compatible
string.

Either add the patch(es) that use the compatible to this series in v2, or put a comment in
the commit message on where we can see the driver changes.

Best regards,
Liviu

-- 
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