linux-kernel - Re: [PATCH v2 3/7] drm/msm/adreno: Implement SMEM-based speed bin

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Message-ID: <bfd6aa32-a28e-47a4-82c7-76c5dd99a44d@linaro.org>
Date: Thu, 18 Apr 2024 11:51:16 +0200
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Rob Clark <robdclark@...il.com>,
 Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 freedreno@...ts.freedesktop.org, devicetree@...r.kernel.org,
 Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v2 3/7] drm/msm/adreno: Implement SMEM-based speed bin

On 18.04.2024 1:43 AM, Dmitry Baryshkov wrote:
> On Wed, Apr 17, 2024 at 10:02:55PM +0200, Konrad Dybcio wrote:
>> On recent (SM8550+) Snapdragon platforms, the GPU speed bin data is
>> abstracted through SMEM, instead of being directly available in a fuse.
>>
>> Add support for SMEM-based speed binning, which includes getting
>> "feature code" and "product code" from said source and parsing them
>> to form something that lets us match OPPs against.
>>
>> Due to the product code being ignored in the context of Adreno on
>> production parts (as of SM8650), hardcode it to SOCINFO_PC_UNKNOWN.
>>
>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>> ---

[...]

>> --- a/drivers/gpu/drm/msm/adreno/adreno_device.c
>> +++ b/drivers/gpu/drm/msm/adreno/adreno_device.c
>> @@ -6,6 +6,8 @@
>>   * Copyright (c) 2014,2017 The Linux Foundation. All rights reserved.
>>   */
>>  
>> +#include <linux/soc/qcom/socinfo.h>
>> +
> 
> Stray leftover?

Looks like

[...]

>> +
>> +#ifdef CONFIG_QCOM_SMEM
> 
> Please extract to a separate function and put the function under ifdef
> (providing a stub otherwise). Having #ifndefs inside funciton body is
> frowned upon.

Hm, this looked quite sparse and straightforward, but I can do that.

[...]

>> +/* As of SM8650, PCODE on production SoCs is meaningless wrt the GPU bin */
>> +#define ADRENO_SKU_ID_FCODE		GENMASK(15, 0)
>> +#define ADRENO_SKU_ID(fcode)	(SOCINFO_PC_UNKNOWN << 16 | fcode)
> 
> If we got rid of PCode matching, is there a need to actually use
> SOCINFO_PC_UNKNOWN here? Or just 0 would be fine?

The IDs need to stay constant for mesa

I used the define here to:

a) define the SKU_ID structure so that it's clear what it's comprised of
b) make it easy to add back Pcode in case it becomes useful with future SoCs
c) avoid mistakes - PC_UNKNOWN happens to be zero, but that's a lucky
   coincidence

We don't *match* based on PCODE, but still need to construct the ID properly

Another option would be to pass the real pcode and add some sort of
"pcode_invalid" property that if found would ignore this part of the
SKU_ID in mesa, but that sounds overly and unnecessarily complex.

Konrad

Konrad