[PATCH 3/5] drm: bridge: Propagate the bus flags from bridge->timings

[Nikhil Devshatwar]

On 14:31-20201021, Tomi Valkeinen wrote:
> On 16/10/2020 13:39, Nikhil Devshatwar wrote:
> > When the next bridge does not specify any bus flags, use the
> > bridge->timings->input_bus_flags as fallback when propagating
> > bus flags from next bridge to current bridge.
> > 
> > Signed-off-by: Nikhil Devshatwar <nikhil.nd at ti.com>
> > ---
> >  drivers/gpu/drm/drm_bridge.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index 64f0effb52ac..8353723323ab 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -975,6 +975,13 @@ drm_atomic_bridge_propagate_bus_flags(struct drm_bridge *bridge,
> >  	 * duplicate the "dummy propagation" logic.
> >  	 */
> >  	bridge_state->input_bus_cfg.flags = output_flags;
> > +
> > +	/*
> > +	 * Use the bridge->timings->input_bus_flags as fallback if the next bridge
> > +	 * does not specify the flags
> > +	 */
> > +	if (!bridge_state->input_bus_cfg.flags)
> > +		bridge_state->input_bus_cfg.flags = bridge->timings->input_bus_flags;
> 
> According to docs, timings can be NULL.
> 
> And, hmm... It's too easy to get confused with these, but... If the bridge defines timings, and
> timings->input_bus_flags != 0, should we always pick that, even if we got something via
> output_flags? Logic being, if this bridge defines timings->input_bus_flags, it probably wants that
> to be used regardless whether we got something from the next bridge.

Got it, the flags from timings if present should be prioritized rather
than treating them as fallback.

Nikhil D

> 
>  Tomi
> 
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