linux-kernel - Re: [PATCH 0/4] Retrieve information about DDR from SMEM

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Message-ID: <0bec3e62-0753-4c3d-abe1-1a43356afc80@oss.qualcomm.com>
Date: Wed, 9 Apr 2025 17:49:53 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>, Kees Cook <kees@...nel.org>,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        Dmitry Baryshkov <lumag@...nel.org>
Cc: Marijn Suijten <marijn.suijten@...ainline.org>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-hardening@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>
Subject: Re: [PATCH 0/4] Retrieve information about DDR from SMEM

On 4/9/25 5:44 PM, Dmitry Baryshkov wrote:
> On 09/04/2025 17:47, Konrad Dybcio wrote:
>> SMEM allows the OS to retrieve information about the DDR memory.
>> Among that information, is a semi-magic value called 'HBB', or Highest
>> Bank address Bit, which multimedia drivers (for hardware like Adreno
>> and MDSS) must retrieve in order to program the IP blocks correctly.
>>
>> This series introduces an API to retrieve that value, uses it in the
>> aforementioned programming sequences and exposes available DDR
>> frequencies in debugfs (to e.g. pass to aoss_qmp debugfs). More
>> information can be exposed in the future, as needed.
> 
> I know that for some platforms HBB differs between GPU and DPU (as it's being programmed currently). Is there a way to check, which values are we going to program:
> 
> - SM6115, SM6350, SM6375 (13 vs 14)
> - SC8180X (15 vs 16)
> - QCM2290 (14 vs 15)

I believe the easiest way is to give them a smoke test.

In any case, unless something is really wrong, any changes made
by this patchset are supposed to be corrections

Konrad