linux-kernel - Re: [PATCH 4/6] drm/msm/adreno: Implement SMEM-based speed bin

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Message-ID: <4c13573e-1398-492a-b2cd-3c5ffee348ff@linaro.org>
Date: Fri, 12 Apr 2024 00:14:13 +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 4/6] drm/msm/adreno: Implement SMEM-based speed bin



On 4/11/24 23:46, Dmitry Baryshkov wrote:
> On Fri, 12 Apr 2024 at 00:35, Konrad Dybcio <konrad.dybcio@...aro.org> wrote:
>>
>>
>>
>> On 4/10/24 21:26, Dmitry Baryshkov wrote:
>>> On Wed, Apr 10, 2024 at 01:42:33PM +0200, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 4/6/24 05:23, Dmitry Baryshkov wrote:
>>>>> On Fri, Apr 05, 2024 at 10:41:32AM +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.
>>>>>>
>>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>>>>> ---
>>>>
>>>> [...]
>>>>
>>>>>
>>>>>> +  }
>>>>>> +
>>>>>> +  ret = qcom_smem_get_product_code(&pcode);
>>>>>> +  if (ret) {
>>>>>> +          dev_err(dev, "Couldn't get product code from SMEM!\n");
>>>>>> +          return ret;
>>>>>> +  }
>>>>>> +
>>>>>> +  /* Don't consider fcode for external feature codes */
>>>>>> +  if (fcode <= SOCINFO_FC_EXT_RESERVE)
>>>>>> +          fcode = SOCINFO_FC_UNKNOWN;
>>>>>> +
>>>>>> +  *speedbin = FIELD_PREP(ADRENO_SKU_ID_PCODE, pcode) |
>>>>>> +              FIELD_PREP(ADRENO_SKU_ID_FCODE, fcode);
>>>>>
>>>>> What about just asking the qcom_smem for the 'gpu_bin' and hiding gory
>>>>> details there? It almost feels that handling raw PCODE / FCODE here is
>>>>> too low-level and a subject to change depending on the socinfo format.
>>>>
>>>> No, the FCODE & PCODE can be interpreted differently across consumers.
>>>
>>> That's why I wrote about asking for 'gpu_bin'.
>>
>> I'd rather keep the magic GPU LUTs inside the adreno driver, especially
>> since not all Snapdragons feature Adreno, but all Adrenos are on
>> Snapdragons (modulo a2xx but I refuse to make design decisions treating
>> these equally to e.g. a6xx)
> 
> LUTs - yes. I wanted to push (FC << a) | (PC << b) and all the RESERVE
> / UNKNOWN magic there.

Ohh this specifically.. yeah I considered pushing that there as well,
but I realized this is specific to the GPU. The socinfo APIs should
only return a valid/unknown code for both P and F and let the consumer
figure out how to interpret these.

> 
>>
>>>
>>>>
>>>>>
>>>>>> +
>>>>>> +  return ret;
>>>>>>     }
>>>>>>     int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>>>>>> @@ -1098,9 +1129,9 @@ int adreno_gpu_init(struct drm_device *drm, struct platform_device *pdev,
>>>>>>                             devm_pm_opp_set_clkname(dev, "core");
>>>>>>             }
>>>>>> -  if (adreno_read_speedbin(dev, &speedbin) || !speedbin)
>>>>>> +  if (adreno_read_speedbin(adreno_gpu, dev, &speedbin) || !speedbin)
>>>>>>                     speedbin = 0xffff;
>>>>>> -  adreno_gpu->speedbin = (uint16_t) (0xffff & speedbin);
>>>>>
>>>>> the &= 0xffff should probably go to the adreno_read_speedbin / nvmem
>>>>> case. WDYT?
>>>>
>>>> Ok, I can keep it, though realistically if this ever does anything
>>>> useful, it likely means the dt is wrong
>>>
>>> Yes, but if DT is wrong, we should probably fail in a sensible way. I
>>> just wanted to point out that previously we had this &0xffff, while your
>>> patch silently removes it.
>>
>> Right, but I don't believe it actually matters.. If that AND ever did
>> anything, this was a silent failure with garbage data passed in anyway.
>>
>> If you really insist, I can remove it separately.
> 
> I'd say, up to Rob or up to your consideration.

Konrad