linux-kernel - Re: [PATCH v8 11/14] firmware: qcom_scm: Add qcom_scm_pas_get_rsc

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Message-ID: <20251208170104.psvk4xxo7b4bg2eo@hu-mojha-hyd.qualcomm.com>
Date: Mon, 8 Dec 2025 22:31:04 +0530
From: Mukesh Ojha <mukesh.ojha@....qualcomm.com>
To: Bjorn Andersson <andersson@...nel.org>
Cc: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Manivannan Sadhasivam <mani@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 11/14] firmware: qcom_scm: Add
 qcom_scm_pas_get_rsc_table() to get resource table

On Fri, Dec 05, 2025 at 04:17:56PM -0600, Bjorn Andersson wrote:
> On Fri, Dec 05, 2025 at 02:15:00PM +0100, Konrad Dybcio wrote:
> > On 12/4/25 1:28 PM, Mukesh Ojha wrote:
> > > On Wed, Dec 03, 2025 at 01:36:32PM +0100, Konrad Dybcio wrote:
> > >> On 11/24/25 4:25 PM, Mukesh Ojha wrote:
> > >>> On Mon, Nov 24, 2025 at 12:48:31PM +0100, Konrad Dybcio wrote:
> > >>>> On 11/21/25 12:01 PM, Mukesh Ojha wrote:
> > >>>>> Qualcomm remote processor may rely on Static and Dynamic resources for
> > >>>>> it to be functional. Static resources are fixed like for example,
> > >>>>> memory-mapped addresses required by the subsystem and dynamic
> > >>>>> resources, such as shared memory in DDR etc., are determined at
> > >>>>> runtime during the boot process.
> > >>>>>
> > >>>>> For most of the Qualcomm SoCs, when run with Gunyah or older QHEE
> > >>>>> hypervisor, all the resources whether it is static or dynamic, is
> > >>>>> managed by the hypervisor. Dynamic resources if it is present for a
> > >>>>> remote processor will always be coming from secure world via SMC call
> > >>>>> while static resources may be present in remote processor firmware
> > >>>>> binary or it may be coming qcom_scm_pas_get_rsc_table() SMC call along
> > >>>>> with dynamic resources.
> > 
> > [...]
> > 
> > > Just to avoid iteration, are you suggesting that we can keep this
> > > guesswork as part of __qcom_scm_pas_get_rsc_table() and start with
> > > something smaller than SZ_16K?
> > > 
> > > I kind of agree with the first part, but SZ_16K was the recommended size
> > > from the firmware for Lemans to start with, in order to pass the SMC
> > > successfully on the first try. However, the same size was failing for
> > > Glymur, and it required a second attempt with the correct size.
> > 
> > It depends on the payload, which you're probably much more familiar with.
> > If 95% of them will be closer to e.g. 1K in size, it perhaps makes sense
> > to use up the additional few dozen cycles on our amazingly fast CPUs and
> > retry as necessary, instead of blindly reserving a whole bunch of memory.
> > 
> 
> Those "few dozen cycles", is tasked with sending messages to RPMh for
> voting and unvoting the buses, then tzmem will hopefully hit the
> genpool, twice, and then radix updates, and then more genpool updated
> and more radix tree work. And then of course there's the one context
> switch to secure world.
> 
> If we don't have space in the genpool, we're going to grow
> dma_alloc_coherent, extend the genpool, call secure world to register
> the new tzmem. And then for all those cases where the allocation wasn't
> enough, the retry (with updated size) will not fit in the
> PAGE_ALIGN(size) genpool that was created, so we'll do this twice.
> 
> Fortunately the tzmem growing should only happen on first remoteproc
> boot, but I think it's a bit optimistic to say "a few dozen"...
> 
> 
> The drawback with making it 16KB is that we're not going to test that
> error path very often. But the more idiomatic form of first calling with
> a size of 0, then allocate and pass the proper size, seems a bit
> wasteful to me as well - in particular if we do it anew each subsystem
> boot.
> 
> PS. 16KB is 0.03% of the ADSP carveout (or 3% of the ADSP DeviceTree
> carveout...).

What you suggest ? 0x36c8 bytes was the size for CDSP resource table on Lemans.

-- 
-Mukesh Ojha