linux-kernel - Re: [PATCH RESEND,v6 2/8] dt-bindings: mailbox: Add property for CMDQ secure driver

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Message-ID: <20240527-bullion-slapping-d35fcddb56d5@spud>
Date: Mon, 27 May 2024 18:36:30 +0100
From: Conor Dooley <conor@...nel.org>
To: "Jason-JH.Lin" <jason-jh.lin@...iatek.com>
Cc: Jassi Brar <jassisinghbrar@...il.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Chun-Kuang Hu <chunkuang.hu@...nel.org>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Conor Dooley <conor+dt@...nel.org>,
	Jason-ch Chen <jason-ch.chen@...iatek.com>,
	Singo Chang <singo.chang@...iatek.com>,
	Nancy Lin <nancy.lin@...iatek.com>,
	Shawn Sung <shawn.sung@...iatek.com>, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org, dri-devel@...ts.freedesktop.org,
	Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH RESEND,v6 2/8] dt-bindings: mailbox: Add property for
 CMDQ secure driver

On Sun, May 26, 2024 at 10:44:37PM +0800, Jason-JH.Lin wrote:
> 1. Add mboxes property to define a GCE loopping thread as a secure IRQ
> handler.
> The CMDQ secure driver requests a mbox channel and sends a looping
> command to the GCE thread. The looping command will wait for a secure
> packet done event signal from secure world and then jump back to the
> first instuction. Each time it waits for an event, it notifies the
> CMDQ driver to perform the same action as the IRQ handler.
> 
> 2. Add gce-events property from gce-props.yaml to define a
> secure packet done signal in secure world.
> There are 1024 events IDs for GCE to use to execute instructions in
> the specific event happened. These events could be signaled by HW or SW
> and their value would be different in different SoC because of HW event
> IDs distribution range from 0 to 1023.
> If we set a static event ID: 855 for mt8188, it might be conflict the
> event ID original set in mt8195.

Two different SoCs, two different compatibles, no problem.
I'm almost certain you previously told me that the firmware changing
could result in a different event ID, but I see no mention of that here.
The commit messages makes it seem like this can be determined by the
compatible, so either give me a commit message that explains why the
compatible is not sufficient or drop the patch.

> So we define an event ID that will be set when GCE runs to the end of
> secure cmdq packet in the secure world.
> 
> This can reduce the latency of software communication between normal
> world and secure world. In addition, we can also remove the complex
> logic after the secure packet done in the secure world.
> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> Signed-off-by: Hsiao Chien Sung <shawn.sung@...iatek.com>
> ---
>  .../devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml b/Documentation/devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml
> index cef9d7601398..6e5e848d61d9 100644
> --- a/Documentation/devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml
> +++ b/Documentation/devicetree/bindings/mailbox/mediatek,gce-mailbox.yaml
> @@ -49,6 +49,10 @@ properties:
>      items:
>        - const: gce
>  
> +  mboxes:
> +    items:
> +      - description: GCE looping thread as a secure IRQ handler

Why is this needed? It's going to be a reference to itself, right?
Why can't you just reserve a channel in the driver?

Thanks,
Conor.

> +
>  required:
>    - compatible
>    - "#mbox-cells"
> @@ -57,6 +61,8 @@ required:
>    - clocks
>  
>  allOf:
> +  - $ref: /schemas/mailbox/mediatek,gce-props.yaml#
> +
>    - if:
>        not:
>          properties:
> @@ -67,7 +73,7 @@ allOf:
>        required:
>          - clock-names
>  
> -additionalProperties: false
> +unevaluatedProperties: false
>  
>  examples:
>    - |
> -- 
> 2.18.0
> 

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