linux-kernel - Re: [PATCH 5/5] drm/msm/a5xx: Enable optional icc voting from OPP tables

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Message-ID: <509a813c-1bc3-8ff9-de2c-26ffe0b92a8a@linaro.org>
Date:   Thu, 23 Feb 2023 00:22:21 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/5] drm/msm/a5xx: Enable optional icc voting from OPP
 tables

On 23/02/2023 00:14, Konrad Dybcio wrote:
> 
> 
> On 22.02.2023 23:12, Dmitry Baryshkov wrote:
>> On 22/02/2023 23:47, Konrad Dybcio wrote:
>>> Add the dev_pm_opp_of_find_icc_paths() call to let the OPP framework
>>> handle bus voting as part of power level setting.
>>
>> This can probably go to the generic code path rather than sticking it into a5xx only.
> The reasoning is explained in the cover letter, a3xx/a4xx already
> have "raw" icc set calls which would require more work (and above
> all, testing) to untangle while keeping backwards compat, this is
> a midterm solution that would allow getting scaling to work earlier.

Those two platforms call icc_set_bw() during setup, however their opp 
tables do not contain BW settings, making dev_pm_opp_of_find_icc_paths() 
nop. So, I think, we might as well call this function on a3xx/a4xx, 
making the code future proof.

> 
> Konrad
>>
>>>
>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>> ---
>>>    drivers/gpu/drm/msm/adreno/a5xx_gpu.c | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
>>> index d09221f97f71..a33af0cc27b6 100644
>>> --- a/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
>>> +++ b/drivers/gpu/drm/msm/adreno/a5xx_gpu.c
>>> @@ -1775,5 +1775,9 @@ struct msm_gpu *a5xx_gpu_init(struct drm_device *dev)
>>>        /* Set up the preemption specific bits and pieces for each ringbuffer */
>>>        a5xx_preempt_init(gpu);
>>>    +    ret = dev_pm_opp_of_find_icc_paths(&pdev->dev, NULL);
>>> +    if (ret)
>>> +        return ERR_PTR(ret);
>>> +
>>>        return gpu;
>>>    }
>>>
>>

-- 
With best wishes
Dmitry