Re: [PATCH v3 1/1] drm: bridge: ti-sn65dsi83: Fix DSI mode flags for stable LVDS output

[tessolveupstream]

On 16-04-2026 14:40, tessolveupstream@xxxxxxxxx wrote:
> 
> 
> On 15-04-2026 12:43, Luca Ceresoli wrote:
>> Hello Sudarshan,
>>
>> On Sun Apr 12, 2026 at 7:38 AM CEST, Sudarshan Shetty wrote:
>>> The current DSI mode configuration enables VIDEO_BURST and disables
>>> horizontal front porch (HFP) and back porch (HBP) transmission using
>>> MIPI_DSI_MODE_VIDEO_NO_HFP and MIPI_DSI_MODE_VIDEO_NO_HBP.
>>>
>>> However, the SN65DSI83/84 bridge relies on receiving full horizontal
>>> timing information over DSI in order to correctly reconstruct the LVDS
>>> output timings. When HFP and HBP are not transmitted, the bridge cannot
>>> recreate the required timing parameters, resulting in unstable or
>>> missing display output on some panels.
>>>
>>> Additionally, while burst mode is supported by the hardware, its use
>>> depends on continuous clock behavior from the DSI host. In practice,
>>> burst mode may introduce instability depending on the host controller
>>> implementation, as the DSI link may transition to low-power state
>>> between bursts.
>>>
>>> In testing, removing burst mode and ensuring full horizontal timing
>>> transmission results in stable LVDS output across affected panels.
>>>
>>> Update the DSI mode flags to:
>>>   - Drop MIPI_DSI_MODE_VIDEO_BURST
>>>   - Drop MIPI_DSI_MODE_VIDEO_NO_HFP
>>>   - Drop MIPI_DSI_MODE_VIDEO_NO_HBP
>>>
>>> This aligns with common system configurations where non-burst mode is
>>> preferred and full timing information is transmitted over DSI.
>>>
>>> Signed-off-by: Sudarshan Shetty <tessolveupstream@xxxxxxxxx>
>>
>> Thanks for having gone into the details and provide a good explanation for
>> the removal of these three flags.
>>
>> It would be still great to have authoritative info from TI, possibly as an
>> update to the documentation.
>>
>> I managed to test on a board with i.MX93, a TI SN65DSI84 and a 1920x1080p60
>> panel, and:
>>
>>  - no image shown with the current mainline driver
>>  - it works by removing only MIPI_DSI_MODE_VIDEO_BURST (my current setup)
>>  - it works with this patch applied
>>
>> Tested-by: Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx> # imx93 1920x1080p60
>>
> 
> Thanks for testing the patch and for the Tested-by tag. 
> I’ll reach out to TI for clarification on the DSI mode flag behavior and
> any documentation updates, and will share any feedback I receive, though I
> cannot guarantee a response.

I had reached out to TI for clarification and any related documentation 
updates, but I have not received any response so far.Given this, it is 
uncertain whether we will be able to obtain further details or official 
confirmation from TI in the near term.

I would appreciate your guidance on how you would prefer us to proceed 
from here.
>> Luca
>>
>> --
>> Luca Ceresoli, Bootlin
>> Embedded Linux and Kernel engineering
>> https://bootlin.com
>