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

[Rob Clark]

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

BR,
-R

> --
> With best wishes
> Dmitry