linux-kernel - Re: [PATCH v2] drm/msm: adreno: a6xx: enable GMU bandwidth voting for x1e80100 GPU

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Message-ID: <4fa44ec5-2792-45e3-af87-b3e4d2ed5d86@oss.qualcomm.com>
Date: Mon, 8 Sep 2025 18:22:05 +0200
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Akhil P Oommen <akhilpo@....qualcomm.com>,
        Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>,
        Rob Clark <robin.clark@....qualcomm.com>, Sean Paul <sean@...rly.run>,
        Konrad Dybcio <konradybcio@...nel.org>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/msm: adreno: a6xx: enable GMU bandwidth voting for
 x1e80100 GPU

On 8/18/25 9:17 AM, Akhil P Oommen wrote:
> On 8/16/2025 3:45 AM, Dmitry Baryshkov wrote:
>> On Thu, Aug 14, 2025 at 07:52:13PM +0200, Konrad Dybcio wrote:
>>> On 8/14/25 6:38 PM, Akhil P Oommen wrote:
>>>> On 8/14/2025 7:56 PM, Neil Armstrong wrote:
>>>>> Hi,
>>>>>
>>>>> On 14/08/2025 13:22, Konrad Dybcio wrote:
>>>>>> On 8/14/25 1:21 PM, Konrad Dybcio wrote:
>>>>>>> On 7/31/25 12:19 PM, Konrad Dybcio wrote:
>>>>>>>> On 7/25/25 10:35 AM, Neil Armstrong wrote:
>>>>>>>>> The Adreno GPU Management Unit (GMU) can also scale DDR Bandwidth
>>>>>>>>> along
>>>>>>>>> the Frequency and Power Domain level, but by default we leave the
>>>>>>>>> OPP core scale the interconnect ddr path.
>>>>>>>>>
>>>>>>>>> Declare the Bus Control Modules (BCMs) and the corresponding
>>>>>>>>> parameters
>>>>>>>>> in the GPU info struct to allow the GMU to vote for the bandwidth.
>>>>>>>>>
>>>>>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
>>>>>>>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>>>>>>>> ---
>>>>>>>>> Changes in v2:
>>>>>>>>> - Used proper ACV perfmode bit/freq
>>>>>>>>> - Link to v1: https://lore.kernel.org/r/20250721-topic-x1e80100-
>>>>>>>>> gpu-bwvote-v1-1-946619b0f73a@...aro.org
>>>>>>>>> ---
>>>>>>>>>   drivers/gpu/drm/msm/adreno/a6xx_catalog.c | 11 +++++++++++
>>>>>>>>>   1 file changed, 11 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c b/drivers/
>>>>>>>>> gpu/drm/msm/adreno/a6xx_catalog.c
>>>>>>>>> index
>>>>>>>>> 00e1afd46b81546eec03e22cda9e9a604f6f3b60..892f98b1f2ae582268adebd758437ff60456cdd5 100644
>>>>>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>>>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_catalog.c
>>>>>>>>> @@ -1440,6 +1440,17 @@ static const struct adreno_info a7xx_gpus[] = {
>>>>>>>>>               .pwrup_reglist = &a7xx_pwrup_reglist,
>>>>>>>>>               .gmu_chipid = 0x7050001,
>>>>>>>>>               .gmu_cgc_mode = 0x00020202,
>>>>>>>>> +            .bcms = (const struct a6xx_bcm[]) {
>>>>>>>>> +                { .name = "SH0", .buswidth = 16 },
>>>>>>>>> +                { .name = "MC0", .buswidth = 4 },
>>>>>>>>> +                {
>>>>>>>>> +                    .name = "ACV",
>>>>>>>>> +                    .fixed = true,
>>>>>>>>> +                    .perfmode = BIT(3),
>>>>>>>>> +                    .perfmode_bw = 16500000,
>>>>>>>>
>>>>>>>> Reviewed-by: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
>>>>>>>
>>>>>>> Actually no, BIT(3) is for the CPU (OS), GPU should use BIT(2)
>>>>
>>>> You are right that BIT(2) is GPU specific, but that support was
>>>> commercialized from A7XX_GEN3. Anyway, the Win KMD uses BIT(2), so lets
>>>> use that in Linux too.
>>>>
>>>> I know some docs show BIT(2) support, but lets not bring in untested
>>>> configurations.
>>>
>>> Eh, then let's get the docs fixed if you don't trust them because we can't
>>> work like that..
>>>
>>> FWIW this is information from per-platform RPMh cmd-db data
>>
>> If it comes from cmd-db, then we should be requesting it from the cmd-db
>> driver rather than hardcoding it here.

No, what I meant is that there is a piece of configuration that reflects
what goes into cmd-db as its compiled and that's where I found that
information

> 
> Not really. This should be under the control of GPU driver.
> BIT(3) is correct for X1E.

BIT(3) is for APPS, see the interconnect driver which also uses it.
This will create conflicts and may cause unvotes when some other
driver requests perf_mode through the ICC API, but the GPU is sitting
idle.

Konrad