linux-kernel - Re: [PATCH 3/6] dt-bindings: gpu: powervr-rogue: Add MediaTek MT8173 GPU

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Message-ID: <cc5847a486a760921375f069a4f65cd29453a624.camel@imgtec.com>
Date: Fri, 31 May 2024 13:37:29 +0000
From: Frank Binns <Frank.Binns@...tec.com>
To: "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "tzimmermann@...e.de"
	<tzimmermann@...e.de>,
        Matt Coster <Matt.Coster@...tec.com>,
        "sboyd@...nel.org" <sboyd@...nel.org>,
        "robh@...nel.org" <robh@...nel.org>,
        "krzk+dt@...nel.org" <krzk+dt@...nel.org>,
        "aford173@...il.com"
	<aford173@...il.com>,
        "maarten.lankhorst@...ux.intel.com"
	<maarten.lankhorst@...ux.intel.com>,
        "wenst@...omium.org"
	<wenst@...omium.org>,
        "mripard@...nel.org" <mripard@...nel.org>,
        "conor+dt@...nel.org" <conor+dt@...nel.org>,
        "angelogioacchino.delregno@...labora.com"
	<angelogioacchino.delregno@...labora.com>
CC: "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "airlied@...il.com" <airlied@...il.com>,
        "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>,
        "linux-mediatek@...ts.infradead.org"
	<linux-mediatek@...ts.infradead.org>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>
Subject: Re: [PATCH 3/6] dt-bindings: gpu: powervr-rogue: Add MediaTek MT8173
 GPU

Hi ChenYu,

On Thu, 2024-05-30 at 16:35 +0800, Chen-Yu Tsai wrote:
> The MediaTek MT8173 comes with a PowerVR Rogue GX6250, which is one
> of the Series6XT GPUs, another sub-family of the Rogue family.

I've added Adam Ford who sent out some DT related patches [1] for the Renesas
variant of GX6250 and the GX6650 (another Series6XT GPU).

> 
> This was part of the very first few versions of the PowerVR submission,
> but was later dropped. The compatible string has been updated to follow
> the new naming scheme adopted for the AXE series.
> 
> In a previous iteration of the PowerVR binding submission [1], the
> number of clocks required for the 6XT family was mentioned to be
> always 3. This is also reflected here.
> 
> [1] https://lore.kernel.org/dri-devel/6eeccb26e09aad67fb30ffcd523c793a43c79c2a.camel@imgtec.com/
> 
> Signed-off-by: Chen-Yu Tsai <wenst@...omium.org>
> ---
>  .../bindings/gpu/img,powervr-rogue.yaml       | 24 +++++++++++++++----
>  1 file changed, 20 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> index 256e252f8087..48aa205b66b4 100644
> --- a/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> +++ b/Documentation/devicetree/bindings/gpu/img,powervr-rogue.yaml
> @@ -12,10 +12,17 @@ maintainers:
>  
>  properties:
>    compatible:
> -    items:
> -      - enum:
> -          - ti,am62-gpu
> -      - const: img,img-axe # IMG AXE GPU model/revision is fully discoverable
> +    oneOf:
> +      - items:
> +          - enum:
> +              - mediatek,mt8173-gpu
> +          # PowerVR 6XT GPU model/revision is fully discoverable
> +          - const: img,powervr-6xt
> +      - items:
> +          - enum:
> +              - ti,am62-gpu
> +          # IMG AXE GPU model/revision is fully discoverable
> +          - const: img,img-axe

The Series6XT GPU models have differing numbers of power domains (either 2, 4 or
5). Whereas, the AXE GPUs have a single power domain, so I assume there should
be a related change here.

The GX6250 has two power domains (lets call them A and B). There's a constraint
that if domain B is powered then domain A must also be powered.

In patch 6 [2] it's setting the power domain to MT8173_POWER_DOMAIN_MFG, which I
believe corresponds to power domain B. I assume this works because the MTK power
controller driver is encoding the constraint above, meaning that when we disable
or enable MT8173_POWER_DOMAIN_MFG it's also disabling/enabling MT8173_POWER_DOMA
IN_MFG_2D (domain A).

Thanks
Frank

[1] https://lists.freedesktop.org/archives/dri-devel/2024-February/443548.html
[2] https://lists.freedesktop.org/archives/dri-devel/2024-May/455833.html

>  
>    reg:
>      maxItems: 1
> @@ -56,6 +63,15 @@ allOf:
>        properties:
>          clocks:
>            maxItems: 1
> +  - if:
> +      properties:
> +        compatible:
> +          contains:
> +            const: img,powervr-6xt
> +    then:
> +      properties:
> +        clocks:
> +          minItems: 3
>  
>  examples:
>    - |