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

[Dmitry Baryshkov]

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 at 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 at 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?

> 
>>>
>>> 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 at quicinc.com>
>>
>>

-- 
With best wishes
Dmitry