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Message-ID: <bc1e71e3-c487-4700-869a-ed21f3633267@linaro.org>
Date: Mon, 16 Dec 2024 10:43:45 +0100
From: neil.armstrong@...aro.org
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
Akhil P Oommen <quic_akhilpo@...cinc.com>, Rob Clark <robdclark@...il.com>,
Sean Paul <sean@...rly.run>, Konrad Dybcio <konradybcio@...nel.org>,
Abhinav Kumar <quic_abhinavk@...cinc.com>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Marijn Suijten <marijn.suijten@...ainline.org>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Bjorn Andersson <andersson@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v5 4/7] drm/msm: adreno: find bandwidth index of OPP and
set it along freq index
On 14/12/2024 00:46, Konrad Dybcio wrote:
> On 13.12.2024 5:55 PM, Akhil P Oommen wrote:
>> On 12/13/2024 10:10 PM, neil.armstrong@...aro.org wrote:
>>> On 13/12/2024 17:31, Konrad Dybcio wrote:
>>>> On 13.12.2024 5:28 PM, neil.armstrong@...aro.org wrote:
>>>>> On 13/12/2024 16:37, Konrad Dybcio wrote:
>>>>>> On 13.12.2024 2:12 PM, Akhil P Oommen wrote:
>>>>>>> On 12/13/2024 3:07 AM, Neil Armstrong wrote:
>>>>>>>> On 12/12/2024 21:21, Konrad Dybcio wrote:
>>>>>>>>> On 11.12.2024 9:29 AM, Neil Armstrong wrote:
>>>>>>>>>> The Adreno GPU Management Unit (GMU) can also scale the DDR
>>>>>>>>>> Bandwidth
>>>>>>>>>> along the Frequency and Power Domain level, until now we left
>>>>>>>>>> the OPP
>>>>>>>>>> core scale the OPP bandwidth via the interconnect path.
>>>>>>>>>>
>>>>>>>>>> In order to enable bandwidth voting via the GPU Management
>>>>>>>>>> Unit (GMU), when an opp is set by devfreq we also look for
>>>>>>>>>> the corresponding bandwidth index in the previously generated
>>>>>>>>>> bw_table and pass this value along the frequency index to the GMU.
>>>>>>>>>>
>>>>>>>>>> The GMU also takes another vote called AB which is a 16bit
>>>>>>>>>> quantized
>>>>>>>>>> value of the floor bandwidth against the maximum supported
>>>>>>>>>> bandwidth.
>>>>>>>>>>
>>>>>>>>>> The AB is calculated with a default 25% of the bandwidth like the
>>>>>>>>>> downstream implementation too inform the GMU firmware the minimal
>>>>>>>>>> quantity of bandwidth we require for this OPP.
>>>>>>>>>>
>>>>>>>>>> Since we now vote for all resources via the GMU, setting the OPP
>>>>>>>>>> is no more needed, so we can completely skip calling
>>>>>>>>>> dev_pm_opp_set_opp() in this situation.
>>>>>>>>>>
>>>>>>>>>> Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
>>>>>>>>>> Reviewed-by: Akhil P Oommen <quic_akhilpo@...cinc.com>
>>>>>>>>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
>>>>>>>>>> ---
>>>>>>>>>> drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 39 +++++++++++++++++
>>>>>>>>>> +++++++
>>>>>>>>>> +++++++++--
>>>>>>>>>> drivers/gpu/drm/msm/adreno/a6xx_gmu.h | 2 +-
>>>>>>>>>> drivers/gpu/drm/msm/adreno/a6xx_hfi.c | 6 +++---
>>>>>>>>>> drivers/gpu/drm/msm/adreno/a6xx_hfi.h | 5 +++++
>>>>>>>>>> 4 files changed, 46 insertions(+), 6 deletions(-)
>>>>>>>>>>
>>>>>>>>>> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/
>>>>>>>>>> gpu/drm/
>>>>>>>>>> msm/adreno/a6xx_gmu.c
>>>>>>>>>> index
>>>>>>>>>> 36696d372a42a27b26a018b19e73bc6d8a4a5235..46ae0ec7a16a41d55755ce04fb32404cdba087be 100644
>>>>>>>>>> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>>>>>>>> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
>>>>>>>>>> @@ -110,9 +110,11 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu,
>>>>>>>>>> struct dev_pm_opp *opp,
>>>>>>>>>> bool suspended)
>>>>>>>>>> {
>>>>>>>>>> struct adreno_gpu *adreno_gpu = to_adreno_gpu(gpu);
>>>>>>>>>> + const struct a6xx_info *info = adreno_gpu->info->a6xx;
>>>>>>>>>> struct a6xx_gpu *a6xx_gpu = to_a6xx_gpu(adreno_gpu);
>>>>>>>>>> struct a6xx_gmu *gmu = &a6xx_gpu->gmu;
>>>>>>>>>> u32 perf_index;
>>>>>>>>>> + u32 bw_index = 0;
>>>>>>>>>> unsigned long gpu_freq;
>>>>>>>>>> int ret = 0;
>>>>>>>>>> @@ -125,6 +127,37 @@ void a6xx_gmu_set_freq(struct msm_gpu
>>>>>>>>>> *gpu,
>>>>>>>>>> struct dev_pm_opp *opp,
>>>>>>>>>> if (gpu_freq == gmu->gpu_freqs[perf_index])
>>>>>>>>>> break;
>>>>>>>>>> + /* If enabled, find the corresponding DDR bandwidth
>>>>>>>>>> index */
>>>>>>>>>> + if (info->bcms && gmu->nr_gpu_bws > 1) {
>>>>>>>>>
>>>>>>>>> if (gmu->nr_gpu_bws)
>>>>>>>>
>>>>>>>> gmu->nr_gpu_bws == 1 means there's not BW in the OPPs (index 0 is the
>>>>>>>> "off" state)
>>>>>>>>
>>>>>>>>>
>>>>>>>>>> + unsigned int bw = dev_pm_opp_get_bw(opp, true, 0);
>>>>>>>>>> +
>>>>>>>>>> + for (bw_index = 0; bw_index < gmu->nr_gpu_bws - 1;
>>>>>>>>>> bw_index+
>>>>>>>>>> +) {
>>>>>>>>>> + if (bw == gmu->gpu_bw_table[bw_index])
>>>>>>>>>> + break;
>>>>>>>>>> + }
>>>>>>>>>> +
>>>>>>>>>> + /* Vote AB as a fraction of the max bandwidth */
>>>>>>>>>> + if (bw) {
>>>>>>>>>
>>>>>>>>> This seems to only be introduced with certain a7xx too.. you should
>>>>>>>>> ping the GMU with HFI_VALUE_GMU_AB_VOTE to check if it's supported
>>>>>>>>
>>>>>>>> Good point
>>>>>>>
>>>>>>> No no. Doing this will trigger some assert in pre-A750 gmu
>>>>>>> firmwares. We
>>>>>>> learned it the hard way. No improvisation please. :)
>>>>>>
>>>>>> We shouldn't be sending that AB data to firmware that doesn't expect
>>>>>> it either too, though..
>>>>>
>>>>> Well we don't !
>>>>
>>>> The code in the scope that I quoted above does that
>>>
>>> No it doesn't, if the proper bcms are not declared in the gpu_info, it
>>> won't
>>
>> I think what Konrad meant was that IB voting is supported from a650+,
>> but AB voting is support only from a750+. So we can add bcm nodes to
>> enable IB voting, but how do we ensure AB voting via GMU is done only on
>> a750+.
>
> Yep, relying on incomplete data in the catalog is not a great way
> to ensure that
I understood correctly, so I'll add a bool to enable AB voting, but please
don't ask me to remove it because it's dead code and useless if only
enabled on a750+...
Neil
>
> Konrad
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