linux-kernel - Re: [PATCH RFC 2/8] drm/msm: adreno: add GMU_BW

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Message-ID: <sgz4h6rlmekiwypaisjbnej326wv4vaqt3mgspp4fs4tg3mdfx@cwmdqcu6gwbf>
Date: Fri, 15 Nov 2024 09:07:49 +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 2/8] drm/msm: adreno: add GMU_BW_VOTE quirk

On Wed, Nov 13, 2024 at 04:48:28PM +0100, Neil Armstrong wrote:
> The Adreno GMU Management Unit (GNU) can also scale the DDR Bandwidth
> along the Frequency and Power Domain level, but by default we leave the
> OPP core vote for the interconnect ddr path.
> 
> While scaling via the interconnect path was sufficient, newer GPUs
> like the A750 requires specific vote paremeters and bandwidth to
> achieve full functionality.
> 
> Add a new Quirk enabling DDR Bandwidth vote via GMU.

Please describe, why this is defined as a quirk rather than a proper
platform-level property. From my experience with 6xx and 7xx, all the
platforms need to send some kind of BW data to the GMU.

> 
> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> ---
>  drivers/gpu/drm/msm/adreno/adreno_gpu.h | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/msm/adreno/adreno_gpu.h b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
> index e71f420f8b3a8e6cfc52dd1c4d5a63ef3704a07f..20b6b7f49473d42751cd4fb4fc82849be42cb807 100644
> --- a/drivers/gpu/drm/msm/adreno/adreno_gpu.h
> +++ b/drivers/gpu/drm/msm/adreno/adreno_gpu.h
> @@ -57,6 +57,7 @@ enum adreno_family {
>  #define ADRENO_QUIRK_HAS_HW_APRIV		BIT(3)
>  #define ADRENO_QUIRK_HAS_CACHED_COHERENT	BIT(4)
>  #define ADRENO_QUIRK_PREEMPTION			BIT(5)
> +#define ADRENO_QUIRK_GMU_BW_VOTE		BIT(6)
>  
>  /* Helper for formating the chip_id in the way that userspace tools like
>   * crashdec expect.
> 
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry