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

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Message-ID: <63a2b391-8b71-41cb-bed2-3bc7fd2154ab@linaro.org>
Date: Fri, 15 Nov 2024 10:21:21 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...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 15/11/2024 08:07, Dmitry Baryshkov wrote:
> 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.

Well APRIV, CACHED_COHERENT & PREEMPTION are HW features, why this can't be part of this ?

Perhaps the "quirks" bitfield should be features instead ?

> 
>>
>> 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
>>
>