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

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Message-ID: <77db4861-4868-4110-8c31-eb2045ddbf4b@oss.qualcomm.com>
Date: Mon, 18 Aug 2025 12:47:17 +0530
From: Akhil P Oommen <akhilpo@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
        Konrad Dybcio <konrad.dybcio@....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 8/16/2025 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.

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

-Akhil.

>