[PATCH v3 4/6] drm/tidss: Set bus_format correctly from bridge/connector

[Nikhil Devshatwar]

On 14:51-20201125, Tomi Valkeinen wrote:
> Hi Nikhil,
> 
> On 19/11/2020 18:01, Nikhil Devshatwar wrote:
> > Remove the old code to iterate over the bridge chain, as this is
> > already done by the framework.
> > The bridge state should have the negotiated bus format and flags.
> > Use these from the bridge's state.
> > If the bridge does not support format negotiation, error out
> > and fail.
> > 
> > Signed-off-by: Nikhil Devshatwar <nikhil.nd at ti.com>
> > Reviewed-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
> > ---
> > 
> > Notes:
> >     changes from v2:
> >     * Remove the old code and use the flags from the bridge state
> > 
> >  drivers/gpu/drm/tidss/tidss_encoder.c | 36 +++++++++++----------------
> >  1 file changed, 14 insertions(+), 22 deletions(-)
> 
> If a first bridge (after the crtc) supports two bus formats as input, how does tidss choose between
> those? This patch just picks bstate->input_bus_cfg.format, and it's not clear to me which one that
> is (the first one?). Also, we don't check if tidss actually supports the bus format.

The selection is done by the framework in
select_bus_fmt_recursive at drivers/gpu/drm/drm_bridge.c:810

My understanding is that currently, the format negotiation logic does
not negotiate all the way till encoder, it stops only at the
first_bridge.

Nikhil Devshatwar

> 
>  Tomi
> 
> -- 
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