Re: [PATCH v2 06/50] drm/msm/dpu: correct sm8550 scaler

[Abhinav Kumar <quic_abhinavk@quicinc.com>]

On 2/25/2023 4:06 PM, Dmitry Baryshkov wrote:
> On 26/02/2023 01:27, Abhinav Kumar wrote:
>> Hi Dmitry
>>
>> On 2/25/2023 3:06 PM, Dmitry Baryshkov wrote:
>>> On 24/02/2023 22:51, Abhinav Kumar wrote:
>>>>
>>>>
>>>> On 2/13/2023 9:36 AM, neil.armstrong@linaro.org wrote:
>>>>> On 13/02/2023 12:16, Dmitry Baryshkov wrote:
>>>>>> On 13/02/2023 12:41, Neil Armstrong wrote:
>>>>>>> On 12/02/2023 00:12, Dmitry Baryshkov wrote:
>>>>>>>> QSEED4 is a newer variant of QSEED3LITE, which should be used on
>>>>>>>> sm8550. Fix the DPU caps structure and used feature masks.
>>>>>>>
>>>>>>> I found nowhere SM8550 uses Qseed4, on downstream DT, it's written:
>>>>>>>          qcom,sde-qseed-sw-lib-rev = "qseedv3lite";
>>>>>>>          qcom,sde-qseed-scalar-version = <0x3002>;
>>>>>>
>>>>>> And then the techpack tells us starting from 0x3000 the v3lite is v4:
>>>>>>
>>>>>> https://git.codelinaro.org/clo/la/platform/vendor/opensource/display-drivers/-/blob/display-kernel.lnx.5.10.r8-rel/msm/sde/sde_hw_util.c#L59 
>>>>>>
>>>>>>
>>>>>> https://git.codelinaro.org/clo/la/platform/vendor/opensource/display-drivers/-/blob/display-kernel.lnx.5.10.r8-rel/msm/sde/sde_hw_util.c#L102 
>>>>>>
>>>>>
>>>>> OK then:
>>>>>
>>>>> Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
>>>>>
>>>>>>
>>>>
>>>> This little bit of confusion is because with downstream, the qseed 
>>>> is a separate usermode library having its own revision. So the SW 
>>>> lib version in this case is not exactly correlating with the scalar 
>>>> HW revision.
>>>
>>> Can you possibly spend some more words here? I see that 
>>> sde_hw_utils.c programs scalers slightly different depending on the 
>>> version of the scaler. At some point the SDE driver was reading the 
>>> register to determine the revision. Then it switched to the revision 
>>> specified in the DTS (which, as far as I understand, corresponds to 
>>> the HW register contents).
>>>
>>> So, where does SW revision come into the play? (and which library are 
>>> we talking about?). Is the 'v3lite' an SW revision? Or is the 0x3002 
>>> an SW revision?
>>>
>>
>> qcom,sde-qseed-sw-lib-rev is the SW library revision for libscale.
>>
>> This is a proprietary library used to calculate the LUTs for the qseed 
>> block. Its not used in the upstream version of the driver.
>>
>> For upstream driver, the driver uses default settings for the LUTs 
>> which work for most of the common use-cases we see.
> 
> Ack, thanks for the explanation. If default settings work, that's good. 
> When you wrote about the proprietary lib, I started wondering if we 
> loose anything (like worse quality of the images, etc).
> 
>>
>> You can refer the below property names, there are programmed by the 
>> lib for the downstream driver.
>>
>> 3733         msm_property_install_range(
>> 3734                 &psde->property_info, "scaler_v2",
>> 3735                 0x0, 0, ~0, 0, PLANE_PROP_SCALER_V2);
>> 3736         msm_property_install_blob(&psde->property_info,
>> 3737                 "lut_sep", 0,
>> 3738                 PLANE_PROP_SCALER_LUT_SEP);
>>
>> No, 0x3002 is the HW revision of the qseed and thats why this change 
>> is correct because the SW library name/rev doesnt exactly match the 
>> qseed HW revision as its possible that even qseed3lite library can 
>> support the QSEED4 HW.
>>
>> So we should be going off qcom,sde-qseed-scalar-version and not 
>> qcom,sde-qseed-sw-lib-rev.
> 
> Thanks!
> 
> So, we should further drop the v3lite/v4 from the scaler name/subblock 
> and use qseed3 everywhere. Correct?
> 

No, even that wont be correct because as you pointed out anything we 
need to handle < QSEED4 case differently from others over here

537 		if (pdpu->pipe_hw->cap->features &
538 			BIT(DPU_SSPP_SCALER_QSEED4)) {
539 			scale_cfg->preload_x[i] = DPU_QSEED4_DEFAULT_PRELOAD_H;
540 			scale_cfg->preload_y[i] = DPU_QSEED4_DEFAULT_PRELOAD_V;
541 		} else {
542 			scale_cfg->preload_x[i] = DPU_QSEED3_DEFAULT_PRELOAD_H;
543 			scale_cfg->preload_y[i] = DPU_QSEED3_DEFAULT_PRELOAD_V;
544 		}


If we want to clean this up more accurately, we should add qseed_rev in 
the dpu caps or rename qseed_type to that which will hold the 0x3xxx 
value and then write a small util which would set the the bit correctly 
based on the qseed rev (0x3xxxx value).


>>
>>>>
>>>> Since upstream DPU only cares about the HW revision of the scaler, 
>>>> we should be going off the qcom,sde-qseed-scalar-version.
>>>>
>>>> This change LGTM,
>>>>
>>>> Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>
>>>
>>>
>