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

[Marek Vasut]

On 8/2/23 20:49, Rob Clark wrote:
> On Wed, Aug 2, 2023 at 11:16 AM Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> wrote:
> > On Wed, 2 Aug 2023 at 20:34, Marek Vasut <marex@xxxxxxx> wrote:
> > > On 8/2/23 15:38, Dmitry Baryshkov wrote:
> > > > On 02/08/2023 11:52, 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>
> > > > > ---
> > > > >    drivers/gpu/drm/bridge/lontium-lt9611.c | 4 +---
> > > > >    1 file changed, 1 insertion(+), 3 deletions(-)
> > > > Acked-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx> #fix db845c
> > > >
> > > > The boards broken by [1] are used in production by different parties
> > > > since 5.10, breaking them doesn't seem more acceptable than breaking the
> > > > new out-of-tree iMX8m hardware.
> > >
> > > The MX8M is also in-tree, so this does not apply.
> >
> > v6.5-rc4:
> >
> > $ git grep lontium,lt9611 | grep -v 9611uxc
> > Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml:$id:
> > http://devicetree.org/schemas/display/bridge/lontium,lt9611.yaml#
> > Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml:
> >      - lontium,lt9611
> > Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml:
> >        compatible = "lontium,lt9611";
> > arch/arm64/boot/dts/qcom/sdm845-db845c.dts: compatible = "lontium,lt9611";
> > drivers/gpu/drm/bridge/lontium-lt9611.c: { "lontium,lt9611", 0 },
> > drivers/gpu/drm/bridge/lontium-lt9611.c: { .compatible = "lontium,lt9611" },
> >
> > next-20230802:
> >
> > $ git grep lontium,lt9611 | grep -v 9611uxc
> > Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml:$id:
> > http://devicetree.org/schemas/display/bridge/lontium,lt9611.yaml#
> > Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml:
> >      - lontium,lt9611
> > Documentation/devicetree/bindings/display/bridge/lontium,lt9611.yaml:
> >        compatible = "lontium,lt9611";
> > arch/arm64/boot/dts/qcom/sdm845-db845c.dts: compatible = "lontium,lt9611";
> > drivers/gpu/drm/bridge/lontium-lt9611.c: { "lontium,lt9611", 0 },
> > drivers/gpu/drm/bridge/lontium-lt9611.c: { .compatible = "lontium,lt9611" },
> >
> > Your device is not in the tree. Your commit broke existing users.
> >
> > Can we please end the argument, land the fix (this revert) for 6.5 and
> > work on the solution for 6.6 or 6.7?
>
> Even if they were in-tree, breaking existing hw means revert and
> try-again.  Especially as we get into later -rc's

Then just apply the revert, I don't have time to debug this right this 
moment, and it is anyway meaningless until I can look at the bus with 
DSI bus analyzer.