Re: [PATCH v3 1/2] drm/bridge: sii902x: Fix mode_valid hook

[Jayesh Choudhary]

On 25/05/24 01:16, Dmitry Baryshkov wrote:
> On Fri, May 24, 2024 at 05:54:02PM +0530, Jayesh Choudhary wrote:
> > Hello Dmitry,
> >
> > On 24/05/24 15:11, Dmitry Baryshkov wrote:
> > > On Fri, May 24, 2024 at 03:05:08PM +0530, Jayesh Choudhary wrote:
> > > > Currently, mode_valid hook returns all mode as valid and it is
> > > > defined only in drm_connector_helper_funcs. With the introduction of
> > > > 'DRM_BRIDGE_ATTACH_NO_CONNECTOR', connector is not initialized in
> > > > bridge_attach call for cases when the encoder has this flag enabled.
> > > > So add the mode_valid hook in drm_bridge_funcs as well with proper
> > > > clock checks for maximum and minimum pixel clock supported by the
> > > > bridge.
> > > >
> > > > Signed-off-by: Jayesh Choudhary <j-choudhary@xxxxxx>
> >
> > [...]
> >
> > > > +
> > > >    static enum drm_mode_status sii902x_mode_valid(struct drm_connector *connector,
> > > >    					       struct drm_display_mode *mode)
> > > >    {
> > > > -	/* TODO: check mode */
> > > > +	struct sii902x *sii902x = connector_to_sii902x(connector);
> > > > +	const struct drm_display_mode *mod = mode;
> > > > -	return MODE_OK;
> > > > +	return sii902x_validate(sii902x, mod);
> > >
> > > There is no need to. The drm_bridge_chain_mode_valid() should take care
> > > of calling bridge's mode_valid callback and rejecting the mode if it is
> > > not accepted.
> >
> > I need some clarity here.
> >
> > IIRC, if the bridge does initialize the connector in case
> > where the encoder does not attach the bridge with the
> > DRM_BRIDGE_ATTACH_NO_CONNECTOR (DBANC) flag (referring to tidss
> > encoder before we implemented the DBANC feature), then
> > drm_connector_helper_func are called and drm_bridge_funcs
> > are NOT called (atleast from what I have seen in detect
> > hook for cdns-mhdp-8546 driver which is there in both
> > structures).
>
> There are different kinds of bridge_funcs. detect is a part of the
> connector-related interface, so it is not called by the drm core. On the
> other hand functions like mode_valid, enable/disable, etc. are called
> for all bridges.

Oh okay!
Thanks for clarifying.

> > I do not have any platform to test non-DBANC encoders.
> > And I did not want to break any platform that were still using
> > bridge_attach without DBANC flag.
> > That is why I kept mode_valid hook in both structures.
> >
> > Are you implying that if connector_helper_funcs are not there
> > then there will be some sort of fallback to bridge_funcs instead
> > of passthrough for mode_valid check? Because that goes against my
> > previous observations.
>
> Not quite. See how drm_atomic_heler uses bridge_funcs.

I will do that and spin another revision with the suggested changes.

Warm Regards,
Jayesh