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

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Message-ID: <2b5f33ba-2108-464c-b4d2-eff2cc6e59cf@linaro.org>
Date: Thu, 18 Apr 2024 13:31:33 +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 1:07 PM, Dmitry Baryshkov wrote:
> On Thu, Apr 18, 2024 at 11:51:16AM +0200, Konrad Dybcio wrote:
>> 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.
> 
> It's fine, just add a comment please. Maybe we can rename PC_UNKNOWN to
> PC_PRODUCTION?

I don't think that's right. The SoC "product code" may actually mean something
(again, not necessarily for Adreno specifically), and with Adreno in mind, it
being only meaningful for engineering samples may change in the future.

Konrad