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

[Luca Ceresoli]

Hello,

On Thu Apr 23, 2026 at 11:16 AM CEST, tessolveupstream wrote:

>> 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.
>
> I followed up with TI, and they pointed us to the relevant sections in the
> SN65DSI83/84/86 datasheets covering DSI video transmission specifications.

Thanks for keeping on! I'm also trying to get info from TI, I'm keeping you
up to date if that will happen.

>> https://www.ti.com/lit/ds/symlink/sn65dsi84.pdf?ts=1776924088430&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FSN65DSI84
>
> As per datasheet Section 7.4.7, the device operates in DSI video mode with
> fixed horizontal timing, where HBP, and HFP are explicitly defined and expected
> to be present as part of the video line structure. The timing description in
> this section assumes standard non‑burst video transmission with all horizontal
> blanking intervals accounted for.
>
> The datasheet does not document support for DSI video burst mode,

This sentence seems incorrect. Section 7.4.7 starts with this sentence:
"The SN65DSI84 supports burst video mode and non-burst video mode ...".

Even though asa matter of fact it looks like many users have issues that
get solved by disabling burst mode.

> nor does it
> mention support for omitting horizontal front or back porch intervals. In
> particular, there is no indication that the device can operate with collapsed
> or suppressed horizontal blanking, as enabled by MIPI_DSI_MODE_VIDEO_BURST,
> MIPI_DSI_MODE_VIDEO_NO_HFP, or MIPI_DSI_MODE_VIDEO_NO_HBP.

This is correct.

We can still try to get TI feedback, but it that won't happen in, say, a
few weeks then I think we should apply this patch.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com