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

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Message-ID: <f00dffa0-11d2-4e88-9770-c34682f770ff@linaro.org>
Date: Mon, 8 Sep 2025 18:33:26 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Akhil P Oommen <akhilpo@....qualcomm.com>,
 Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: 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 08/09/2025 18:29, Akhil P Oommen wrote:
> On 9/8/2025 9:52 PM, Konrad Dybcio wrote:
>> 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.

Yeah gpu will vote via it's own bcm drv interface and they will be agregated in the rpmh.

It's basically the whole point of this gpu bandwidth voting via gmu.

> 
> No. GPU vote goes via a different DRV. So it is independent. Anyway, I
> checked this further earlier. X1E platform doesn't implement any
> perfmode vote. So both BIT(3) and BIT(2) are no-op and are ignored by
> AOSS. ICC driver's vote too should be no-op on X1E.

So I can drop the ACV bcm or it's a compat for other SoCs ?

Neil

> 
> -Akhil.
> 
>>
>> Konrad
>