linux-kernel - Re: [PATCH v2 08/11] drm/msm: adreno: request for maximum bus bandwidth usage

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Message-ID: <20241123225954.lv3k2fxk7rxyh67z@hu-akhilpo-hyd.qualcomm.com>
Date: Sun, 24 Nov 2024 04:29:54 +0530
From: Akhil P Oommen <quic_akhilpo@...cinc.com>
To: Neil Armstrong <neil.armstrong@...aro.org>
CC: 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>,
        "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>,
        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 v2 08/11] drm/msm: adreno: request for maximum bus
 bandwidth usage

On Tue, Nov 19, 2024 at 06:56:43PM +0100, Neil Armstrong wrote:
> When requesting a DDR bandwidth level along a GPU frequency
> level via the GMU, we can also specify the bus bandwidth usage in a 16bit
> quantitized value.
> 
> For now simply request the maximum bus usage.

Why? You don't care about power efficiency?
Lets drop this patch. We don't care about AB vote yet.

-Akhil

> 
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>  drivers/gpu/drm/msm/adreno/a6xx_gmu.c | 11 +++++++++++
>  drivers/gpu/drm/msm/adreno/a6xx_hfi.h |  5 +++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> index dc2d0035544e7848e5c4ea27f1ea9a191f9c4991..36c0f67fd8e109aabf09a0804bacbed3593c39d7 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_gmu.c
> @@ -134,6 +134,17 @@ void a6xx_gmu_set_freq(struct msm_gpu *gpu, struct dev_pm_opp *opp,
>  			if (bw == gmu->gpu_bw_table[bw_index])
>  				break;
>  		}
> +
> +		if (bw_index) {
> +			/*
> +			 * Append AB vote to the maximum bus usage.
> +			 * AB represents a quantitized 16bit value of the
> +			 * max ddr bandwidth we could use, let's simply
> +			 * request the maximum for now.
> +			 */
> +			bw_index |= AB_VOTE(MAX_AB_VOTE);
> +			bw_index |= AB_VOTE_ENABLE;
> +		}
>  	}
>  
>  	gmu->current_perf_index = perf_index;
> diff --git a/drivers/gpu/drm/msm/adreno/a6xx_hfi.h b/drivers/gpu/drm/msm/adreno/a6xx_hfi.h
> index 528110169398f69f16443a29a1594d19c36fb595..52ba4a07d7b9a709289acd244a751ace9bdaab5d 100644
> --- a/drivers/gpu/drm/msm/adreno/a6xx_hfi.h
> +++ b/drivers/gpu/drm/msm/adreno/a6xx_hfi.h
> @@ -173,6 +173,11 @@ struct a6xx_hfi_gx_bw_perf_vote_cmd {
>  	u32 bw;
>  };
>  
> +#define AB_VOTE_MASK		GENMASK(31, 16)
> +#define MAX_AB_VOTE		(FIELD_MAX(AB_VOTE_MASK) - 1)
> +#define AB_VOTE(vote)		FIELD_PREP(AB_VOTE_MASK, (vote))
> +#define AB_VOTE_ENABLE		BIT(8)
> +
>  #define HFI_H2F_MSG_PREPARE_SLUMBER 33
>  
>  struct a6xx_hfi_prep_slumber_cmd {
> 
> -- 
> 2.34.1
>