linux-kernel - Re: [PATCH v2 06/11] remoteproc: Move resource table data structure to its own header

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Message-ID: <20250820151822.6cmowxfsheqxfrnb@hu-mojha-hyd.qualcomm.com>
Date: Wed, 20 Aug 2025 20:48:22 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Vikash Garodia <quic_vgarodia@...cinc.com>,
        Dikshita Agarwal <quic_dikshita@...cinc.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-media@...r.kernel.org, linux-remoteproc@...r.kernel.org
Subject: Re: [PATCH v2 06/11] remoteproc: Move resource table data structure
 to its own header

On Wed, Aug 20, 2025 at 10:12:15AM +0200, Stephan Gerhold wrote:
> On Tue, Aug 19, 2025 at 10:24:41PM +0530, Mukesh Ojha wrote:
> > The resource table data structure has traditionally been associated with
> > the remoteproc framework, where the resource table is included as a
> > section within the remote processor firmware binary. However, it is also
> > possible to obtain the resource table through other means—such as from a
> > reserved memory region populated by the boot firmware, statically
> > maintained driver data, or via a secure SMC call—when it is not embedded
> > in the firmware.
> > 
> > There are multiple Qualcomm remote processors (e.g., Venus, Iris, GPU,
> > etc.) in the upstream kernel that do not use the remoteproc framework to
> > manage their lifecycle for various reasons.
> > 
> > When Linux is running at EL2, similar to the Qualcomm PAS driver
> > (qcom_q6v5_pas.c), client drivers for subsystems like video and GPU may
> > also want to use the resource table SMC call to retrieve and map
> > resources before they are used by the remote processor.
> > 
> 
> All the examples you give here (Venus/Iris, GPU) have some sort of EL2
> support already for older platforms:

Example was taken from perspective of remote processor life-cycle management.
You are right they have worked before in non-secure way for Chrome.

> 
>  - For GPU, we just skip loading the ZAP shader and access the protected
>    registers directly. I would expect the ZAP shader does effectively
>    the same, perhaps with some additional handling for secure mode. Is
>    this even a real remote processor that has a separate IOMMU domain?
> 

I don't think it is the case and think the same that they can skip
loading and Hence, I have not yet added support for it.

Will check internally before doing anything on GPU.

>  - For Venus/Iris, there is code upstream similar to your PATCH 11/11
>    that maps the firmware with the IOMMU (but invokes reset directly
>    using the registers, without using PAS). There is no resource table
>    used for that either, so at least all Venus/Iris versions so far
>    apparently had no need for any mappings aside from the firmware
>    binary.

You are absolutely right

> 
> I understand that you want to continue using PAS for these, but I'm a
> bit confused what kind of mappings we would expect to have in the
> resource table for video and GPU. Could you give an example?

We have some debug hw tracing available for video for lemans, which is
optional However, I believe infra is good to have incase we need some
required resources to be map for Video to work for a SoC.

> 
> Thanks,
> Stephan

-- 
-Mukesh Ojha