linux-kernel - Re: [PATCH v3 4/7] drm/msm: adreno: find bandwidth index of OPP and set it along freq index

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Message-ID: <e3bb3f66-9cad-40a4-ab55-f1d5a8e34d4d@oss.qualcomm.com>
Date: Fri, 29 Nov 2024 16:33:36 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Neil Armstrong <neil.armstrong@...aro.org>,
        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>,
        Akhil P Oommen <quic_akhilpo@...cinc.com>
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 v3 4/7] drm/msm: adreno: find bandwidth index of OPP and
 set it along freq index

On 28.11.2024 11:25 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 AB pre-calculated vote is appended to the bandwidth index
> to inform the GMU firmware the quantity of bandwidth we need.
> 
> 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.
> 
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 23 +++++++++++++++++++++--
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  2 +-
>  drivers/gpu/drm/msm/adreno/a6xx_hfi.c |  6 +++---
>  3 files changed, 25 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index ee2010a01186721dd377f1655fcf05ddaff77131..c09442ecc861c4e56c81e7e775b9e57baf7d2e51 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 +127,21 @@ 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) {
> +		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;
> +		}
> +
> +		if (bw_index) {
> +			bw_index |= AB_VOTE(gmu->gpu_ab_votes[bw_index]);
> +			bw_index |= AB_VOTE_ENABLE;
> +		}
> +	}

If we couple frequency levels with bw levels (i.e. duplicate the highest
bandwidth a couple times), we can drop all this search logic..

> +
>  	gmu->current_perf_index = perf_index;
>  	gmu->freq = gmu->gpu_freqs[perf_index];
>  
> @@ -140,8 +157,10 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp,
>  		return;
>  
>  	if (!gmu->legacy) {
> -		a6xx_hfi_set_freq(gmu, perf_index);
> -		dev_pm_opp_set_opp(&gpu->pdev->dev, opp);
> +		a6xx_hfi_set_freq(gmu, perf_index, bw_index);
> +		/* With Bandwidth voting, we now vote for all resources, so skip OPP set */
> +		if (!bw_index)
> +			dev_pm_opp_set_opp(&gpu->pdev->dev, opp);

..and then it would come down to..

if (!info->bcms)

Konrad