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

[Marek Vasut]

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.