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

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Message-ID: <aKWDXySSt57tXHVP@linaro.org>
Date: Wed, 20 Aug 2025 10:12:15 +0200
From: Stephan Gerhold <stephan.gerhold@...aro.org>
To: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
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 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:

 - 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?

 - 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.

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?

Thanks,
Stephan