linux-kernel - Re: [PATCH RFC 5/8] drm/msm: adreno: find bandwidth index of OPP and set it along freq index

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Message-ID: <ith6te3m4cjwjyxrsxpjsvqsyjr3qrmlyyo7cucljuweuzn37b@lmd5b5mqwkbw>
Date: Fri, 15 Nov 2024 09:28:23 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Neil Armstrong <neil.armstrong@...aro.org>
Cc: Akhil P Oommen <quic_akhilpo@...cinc.com>, 
	Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>, Stephen Boyd <sboyd@...nel.org>, 
	"Rafael J. Wysocki" <rafael@...nel.org>, Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>, 
	Konrad Dybcio <konradybcio@...nel.org>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	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>, Connor Abbott <cwabbott0@...il.com>, linux-pm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org
Subject: Re: [PATCH RFC 5/8] drm/msm: adreno: find bandwidth index of OPP and
 set it along freq index

On Wed, Nov 13, 2024 at 04:48:31PM +0100, Neil Armstrong wrote:
> The Adreno GMU 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.
> 
> 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 | 17 +++++++++++++++--
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.h |  2 +-
>  drivers/gpu/drm/msm/adreno/a6xx_hfi.c |  6 +++---
>  3 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index 504a7c5d5a9df4c787951f2ae3a69d566d205ad5..1131c3521ebbb0d053aceb162052ed01e197726a 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -113,6 +113,7 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp,
>  	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 +126,16 @@ 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 ((adreno_gpu->info->quirks & ADRENO_QUIRK_GMU_BW_VOTE) && gmu->nr_gpu_bws) {
> +		unsigned int bw = dev_pm_opp_get_bandwidth(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;
> +		}
> +	}
> +
>  	gmu->current_perf_index = perf_index;
>  	gmu->freq = gmu->gpu_freqs[perf_index];
>  
> @@ -140,8 +151,10 @@ 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)

if (!bw_index) ???

Also should there be a 0 vote too in case we are shutting down /
suspending?

> +			dev_pm_opp_set_opp(&gpu->pdev->dev, opp);
>  		return;
>  	}
>  
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> index 95c632d8987a517f067c48c61c6c06b9a4f61fc0..9b4f2b1a0c48a133cd5c48713bc321c74eaffce9 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.h
> @@ -205,7 +205,7 @@ void a6xx_hfi_init(struct a6xx_gmu *gmu);
>  int a6xx_hfi_start(struct a6xx_gmu *gmu, int boot_state);
>  void a6xx_hfi_stop(struct a6xx_gmu *gmu);
>  int a6xx_hfi_send_prep_slumber(struct a6xx_gmu *gmu);
> -int a6xx_hfi_set_freq(struct a6xx_gmu *gmu, int index);
> +int a6xx_hfi_set_freq(struct a6xx_gmu *gmu, int perf_index, int bw_index);
>  
>  bool a6xx_gmu_gx_is_on(struct a6xx_gmu *gmu);
>  bool a6xx_gmu_sptprac_is_on(struct a6xx_gmu *gmu);
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> index 9a89ba95843e7805d78f0e5ddbe328677b6431dd..e2325c15677f1a1194a811e6ecbb5931bdfb1ad9 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.c
> @@ -752,13 +752,13 @@ static int a6xx_hfi_send_core_fw_start(struct a6xx_gmu *gmu)
>  		sizeof(msg), NULL, 0);
>  }
>  
> -int a6xx_hfi_set_freq(struct a6xx_gmu *gmu, int index)
> +int a6xx_hfi_set_freq(struct a6xx_gmu *gmu, int freq_index, int bw_index)
>  {
>  	struct a6xx_hfi_gx_bw_perf_vote_cmd msg = { 0 };
>  
>  	msg.ack_type = 1; /* blocking */
> -	msg.freq = index;
> -	msg.bw = 0; /* TODO: bus scaling */
> +	msg.freq = freq_index;
> +	msg.bw = bw_index;
>  
>  	return a6xx_hfi_send_msg(gmu, HFI_H2F_MSG_GX_BW_PERF_VOTE, &msg,
>  		sizeof(msg), NULL, 0);
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry