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

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Message-ID: <CAA8EJpq1KhxPTaQY_Bra0xwC7V6ftr+cAH0CdHgzkU93YksaPA@mail.gmail.com>
Date:   Wed, 2 Aug 2023 21:12:00 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Marek Vasut <marex@...x.de>
Cc:     neil.armstrong@...aro.org, Andrzej Hajda <andrzej.hajda@...el.com>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jagan Teki <jagan@...rulasolutions.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Amit Pundir <amit.pundir@...aro.org>
Subject: Re: [PATCH] Revert "drm/bridge: lt9611: Do not generate HFP/HBP/HSA
 and EOT packet"

On Wed, 2 Aug 2023 at 20:34, Marek Vasut <marex@...x.de> wrote:
>
> 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@...x.de>
> >>>> Cc: Robert Foss <rfoss@...nel.org>
> >>>> Cc: Jagan Teki <jagan@...rulasolutions.com>
> >>>> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> >>>> Cc: Abhinav Kumar <quic_abhinavk@...cinc.com>
> >>>> Fixes: 8ddce13ae69 ("drm/bridge: lt9611: Do not generate HFP/HBP/HSA
> >>>> and EOT packet")
> >>>> Reported-by: Amit Pundir <amit.pundir@...aro.org>
> >>>> Link:
> >>>> https://lore.kernel.org/r/CAMi1Hd0TD=2z_=bcDrht3H_wiLvAFcv8Z-U_r_KUOoeMc6UMjw@mail.gmail.com/
> >>>> Signed-off-by: Neil Armstrong <neil.armstrong@...aro.org>
> >>>
> >>> 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.

We proposed another one.

-- 
With best wishes
Dmitry