[PATCH 2/2] drm/bridge: lt9611: Do not generate HFP/HBP/HSA and EOT packet

[Marek Vasut]

On 8/2/23 10:39, neil.armstrong at linaro.org wrote:
> Hi Marek,

Hi,

> On 13/07/2023 20:28, Marek Vasut wrote:
> 
> <snip>
> 
>>>>
>>>> MIPI_DSI_MODE_VIDEO_NO_HFP means the HBP period is just skipped by 
>>>> DSIM.
>>>>
>>>> Maybe there is a need for new set of flags which differentiate 
>>>> between HBP skipped (i.e. NO HBP) and HBP LP11 ?
>>>>
>>>
>>> No, the section of the MIPI DSI spec I posted below clearly states 
>>> there are two options:
>>>
>>> 1) send blanking packets during those periods
>>> 2) transition to LP11 during those periods
>>>
>>> There is no 3rd option in the spec of not doing both like what you 
>>> are suggesting. So DSIM should also be only transitioning to LP11 
>>> during those periods if its not sending the blanking packets with 
>>> those flags set.
>>>
>>> So, there is no need for any new set of flags to differentiate.
>>>
>>> The flags and their interpretation is correct in MSM driver. I cannot 
>>> comment on what exactly DSIM does with those flags.
>>
>> How do you explain the comment in include/drm/drm_mipi_dsi.h:
>>
>> 128 /* disable hback-porch area */
>> 129 #define MIPI_DSI_MODE_VIDEO_NO_HBP      BIT(6)
> 
> Can you specify how you determined those flags were needed on DSIM ? a 
> vendor tree ? a datasheet ?

The following upstream commit:

996e1defca344 ("drm: exynos: dsi: Fix MIPI_DSI*_NO_* mode flags")

> In the meantime, we should revert this patch because it regresses some Qcom
> based platforms until we figure out what's missing to make DSIM based 
> boards
> happy.
> 
> I'll send a revert change afterwards.

That change would break existing use case on i.MX8M then, I disagree 
with that revert.