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

[Marek Vasut]

On 8/2/23 14:38, Dmitry Baryshkov wrote:
> On 02/08/2023 15:07, 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 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.
>
> Up to now we saw no proof that MSM incorrectly implements the flags.

Please read the whole "[PATCH 2/2] drm/bridge: lt9611: Do not generate 
HFP/HBP/HSA and EOT packet" discussion for context.