Re: [PATCH v2] drm/bridge: dw-hdmi: use safe format when first in bridge chain

[Neil Armstrong]

Hi,

On 04/02/2022 15:05, Robert Foss wrote:
> On Wed, 19 Jan 2022 at 13:28, Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:
> > When the dw-hdmi bridge is in first place of the bridge chain, this
> > means there is no way to select an input format of the dw-hdmi HW
> > component.
> >
> > Since introduction of display-connector, negotiation was broken since
> > the dw-hdmi negotiation code only worked when the dw-hdmi bridge was
> > in last position of the bridge chain or behind another bridge also
> > supporting input & output format negotiation.
> >
> > Commit 0656d1285b79 ("drm/bridge: display-connector: implement bus fmts callbacks")
>
> I think this is the wrong hash. Is 7cd70656d128 the actual hash?

Wow indeed, thanks for checking...

> > was introduced to make negotiation work again by making display-connector
> > act as a pass-through concerning input & output format negotiation.
> >
> > But in the case where the dw-hdmi is single in the bridge chain, for
> > example on Renesas SoCs, with the display-connector bridge the dw-hdmi
> > is no more single, breaking output format.
> >
> > Reported-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> > Bisected-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> > Tested-by: Kieran Bingham <kieran.bingham+renesas@xxxxxxxxxxxxxxxx>
> > Fixes: 0656d1285b79 ("drm/bridge: display-connector: implement bus fmts callbacks").
>
> This hash too.
>
> > Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> > ---
> > Changes since v1:
> > - Remove bad fix in dw_hdmi_bridge_atomic_get_input_bus_fmts
> > - Fix typos in commit message
> >
> >   drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > index 54d8fdad395f..97cdc61b57f6 100644
> > --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> > @@ -2551,8 +2551,9 @@ static u32 *dw_hdmi_bridge_atomic_get_output_bus_fmts(struct drm_bridge *bridge,
> >          if (!output_fmts)
> >                  return NULL;
> >
> > -       /* If dw-hdmi is the only bridge, avoid negociating with ourselves */
> > -       if (list_is_singular(&bridge->encoder->bridge_chain)) {
> > +       /* If dw-hdmi is the first or only bridge, avoid negociating with ourselves */
> > +       if (list_is_singular(&bridge->encoder->bridge_chain) ||
> > +           list_is_first(&bridge->chain_node, &bridge->encoder->bridge_chain)) {
> >                  *num_output_fmts = 1;
> >                  output_fmts[0] = MEDIA_BUS_FMT_FIXED;
> >
> > --
> > 2.25.1
>
> There are two checkstyle issues apart from the above mentioned hash
> issues, and I think we can ignore those. With the above mentioned
> issue fixed, feel free to add my r-b.
>
> Reviewed-by: Robert Foss <robert.foss@xxxxxxxxxx>

Thanks, I'll fix & resend with your r-b.

Neil