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

From: Marek Vasut
Date: Wed Aug 02 2023 - 13:36:43 EST


On 8/2/23 14:37, Neil Armstrong wrote:
On 02/08/2023 14:28, Marek Vasut wrote:
On 8/2/23 14:07, Marek Vasut wrote:
On 8/2/23 10:52, Neil Armstrong wrote:
This reverts commit [1] to fix display regression on the Dragonboard 845c
(SDM845) devboard.

There's a mismatch on the real action of the following flags:
- MIPI_DSI_MODE_VIDEO_NO_HSA
- MIPI_DSI_MODE_VIDEO_NO_HFP
- MIPI_DSI_MODE_VIDEO_NO_HBP
which leads to a non-working display on qcom platforms.

[1] 8ddce13ae696 ("drm/bridge: lt9611: Do not generate HFP/HBP/HSA and EOT packet")

Cc: Marek Vasut <marex@xxxxxxx>
Cc: Robert Foss <rfoss@xxxxxxxxxx>
Cc: Jagan Teki <jagan@xxxxxxxxxxxxxxxxxxxx>
Cc: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Cc: Abhinav Kumar <quic_abhinavk@xxxxxxxxxxx>
Fixes: 8ddce13ae69 ("drm/bridge: lt9611: Do not generate HFP/HBP/HSA and EOT packet")
Reported-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
Link: https://lore.kernel.org/r/CAMi1Hd0TD=2z_=bcDrht3H_wiLvAFcv8Z-U_r_KUOoeMc6UMjw@xxxxxxxxxxxxxx/
Signed-off-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>

This breaks LT9611 operation on i.MX8M Mini/Nano/Plus, so, NAK.

I am currently using this LT9611 with Linux 6.1.y

Correction, 6.1.y only with the DSIM patches backported.

Well you'll need to keep [1] backported on your downstream branch,
this revert won't propagate to v6.1 stable anyway.

I will still have a problem with those MX8M boards during my development on linux-next, so that isn't helping.

in production and this is not acceptable. I also believe the correct fix is on the MSM side, not on the LT9611 driver side, since MSM incorrectly implements these flags.


Since [1] breaks Qcom boards on v6.5, and [1] was added for v6.5 to make the bridge work
on i.MX8M Mini/Nano/Plus, it's not acceptable either to keep it for the v6.5 release.

So, we need to find a solution which works for both, I proposed one already.