[PATCH 1/2] drm/msm/dpu: fix DSC 1.2 block lengths

[Dmitry Baryshkov]

On 23/06/2023 22:37, Abhinav Kumar wrote:
> 
> 
> On 6/23/2023 4:37 AM, Dmitry Baryshkov wrote:
>> On 23/06/2023 09:54, Marijn Suijten wrote:
>>> On 2023-06-22 22:47:04, Abhinav Kumar wrote:
>>>> On 6/22/2023 6:37 PM, Dmitry Baryshkov wrote:
>>>>> All DSC_BLK_1_2 declarations incorrectly pass 0x29c as the block 
>>>>> length.
>>>>> This includes the common block itself, enc subblocks and some empty
>>>>> space around. Change that to pass 0x4 instead, the length of common
>>>>> register block itself.
>>>>>
>>>>> Fixes: 0d1b10c63346 ("drm/msm/dpu: add DSC 1.2 hw blocks for 
>>>>> relevant chipsets")
>>>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov at linaro.org>
>>>>
>>>> There is no need of a fixes tag for this.
>>>>
>>>> This is not a bug but was intentional.
>>>>
>>>> Till we added sub-block parsing support we had to dump the whole block.
>>>>
>>>> And hence I would suggest this change should be merged after the
>>>> sub-block parsing change otherwise we wont have full register dumps 
>>>> for DSC.
>>>
>>> This was indeed intentional, we discussed it in [1].
>>>
>>> In fact I asked to make it 0xf00 + 0x10 or 0xf80 + 0x10 to also cover
>>> the CTL registers, but that change didn't make it through.  0x29c is an
>>> arbitrary number that I have no clue what it was based on.
>>
>> This should have been NAKed. or at least TODOed.
>>
> 
> Its is not an arbitrary number. Thats an incorrect comment.
> 
> Its 4 more than the encoder's last offset which is 0x298 + 0x4 = 0x29c.
> 
> There was nothing to NAK or TODO here.

We do not include sub-blocks in the main block area. The SSPP's SRC 
blocks were cleaned up for this reason. The ENC registers are definitely 
a sub-block (and are described this way). There should have been a 
"TODO: reduce block length to 0x4 after adding sub-blocks to dump" comment.

> 
>>>
>>> [1]: 
>>> https://lore.kernel.org/linux-arm-msm/y2whfntyo2rbrg3taazjdw5sijle6k6swzl4uutcxm6tmuayh4@uxdur74uasua/
>>>
>>> - Marijn
>>

-- 
With best wishes
Dmitry