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

[tessolveupstream@gmail.com]

On 20-05-2026 17:08, Luca Ceresoli wrote:
> Hello,
> 
> On Wed May 20, 2026 at 11:04 AM CEST, tessolveupstream wrote:
> 
> [...]
> 
>>>> We have not received any further updates from TI regarding this issue, and
>>>> at this point, we are not sure if we will get additional feedback from them.
>>>> As you had mentioned earlier that the patch could be considered after
>>>> waiting for some time, could you please let us know how we can proceed
>>>> further from here?
>>>
>>> I am getting some feedback from TI, but it is taking some time.
>>>
>>> For the time being I think it is clear that HBP and HFP are required, and
>>> so removing the MIPI_DSI_MODE_VIDEO_NO_HFP and MIPI_DSI_MODE_VIDEO_NO_HBP
>>> in your patch seems to be fully correct, even though this had no effect on
>>> the panel I tested.
>>>
>>> I'm still trying to get some better info to ensure that switching from
>>> burst mode to non-burst mode is not expected to have side effects.
>>>
>>> For thi reason, I think it would be great if you could send a new version
>>> with two separate patches: the first one enabling HFP and HBP and which can
>>> be applied right away, the second to disable burst mode for which I'd wait
>>> a bit longer for TI feedback. You can keep the Tested-by lines.
>>>
>>
>> Thanks for the clarification. I just wanted to confirm my understanding
>> regarding the patch split you suggested.
>>
>> From your comments, my understanding is that the first patch would only
>> enable HFP and HBP by removing MIPI_DSI_MODE_VIDEO_NO_HFP and
>> MIPI_DSI_MODE_VIDEO_NO_HBP, while keeping burst mode enabled, so the mode
>> flags would become:
>>
>> dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
>>           MIPI_DSI_MODE_VIDEO_NO_HSA | MIPI_DSI_MODE_NO_EOT_PACKET;
>>
>> Then, the second patch would only disable burst mode, resulting in:
>>
>> dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_NO_HSA |
>>           MIPI_DSI_MODE_NO_EOT_PACKET;
>>
>> Could you please confirm whether my understanding is correct?
> 
> Yes, correct.
>

Thank you for the clarification. 
>> Also, from our testing, when using:
>>
>> dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
>>           MIPI_DSI_MODE_VIDEO_NO_HSA | MIPI_DSI_MODE_NO_EOT_PACKET;
>>
>> we are not able to get display output.
> 
> This is the case for the panel I worked on as well. In the practice we both
> observe that non-burst mode is what fixes the panel, but there is no clear
> explanation of the reason in the docs (that's what I hope to discover from
> TI).
> 
> On the other hand the HBP and HFP are clearly required by the docs, so it
> should be fine to enable those without waiting for further info from
> TI. This is not fixing your and my panel, but it's a fix, no doubt.
> 
>> I just wanted to mention this
>> observation in case it is relevant to the patch split discussion.
>>
>> Additionally, regarding the Tested-by tags you mentioned earlier,
>> should I carry them forward to both patches, or would you prefer them
>> only on the applicable patch?
> 
> I'd say yes. People who sent these tags have tested a patch that is the sum
> of the two future patches, so I'd say it's OK to keep the R-by on both
> patches.
> 

Okay, I just wanted to confirm one point — when you mentioned R-by, are you 
referring to the Reviewed-by tag? I wanted to make sure I understood it 
correctly before carrying the tags forward in the next version. 🙂> Thanks for your patience. We'll get to the bottom of this issue! :)
> 
> Luca
> 
> --
> Luca Ceresoli, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com