[PATCH] drm: rcar-du: dw-hdmi: Reject modes with a too high clock frequency

[Laurent Pinchart]

Hi Kieran,

On Friday, 23 November 2018 16:43:28 EET Kieran Bingham wrote:
> On 23/11/2018 14:34, Laurent Pinchart wrote:
> > Implement a .mode_valid() handler in the R-Car glue layer to reject
> > modes with an unsupported clock frequency.
> > 
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas at ideasonboard.com>
> > ---
> > 
> >  drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> > b/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c index 75490a3e0a2a..8a603235f22d
> > 100644
> > --- a/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> > +++ b/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> > @@ -35,6 +35,16 @@ static const struct rcar_hdmi_phy_params
> > rcar_hdmi_phy_params[] = {
> >  	{ ~0UL,      0x0000, 0x0000, 0x0000 },
> >  
> >  };
> > 
> > +static enum drm_mode_status
> > +rcar_hdmi_mode_valid(struct drm_connector *connector,
> > +		     const struct drm_display_mode *mode)
> > +{
> > +	if (mode->clock > 297000)
> 
> Is 29700 constant? Can it be determined from any other location or is it
> just a magically known platform value?

It's the last entry of the rcar_hdmi_phy_params table above. I considered 
writing it

	if (mode->clock > 
rcar_hdmi_phy_params[ARRAY_SIZE(rcar_hdmi_phy_params)-2].mpixelclock)

but found it a but hard to parse. Do you think it would be better ?

> > +		return MODE_CLOCK_HIGH;
> > +
> > +	return MODE_OK;
> > +}
> > +
> > 
> >  static int rcar_hdmi_phy_configure(struct dw_hdmi *hdmi,
> >  				   const struct dw_hdmi_plat_data *pdata,
> >  				   unsigned long mpixelclock)
> > @@ -59,6 +69,7 @@ static int rcar_hdmi_phy_configure(struct dw_hdmi *hdmi,
> >  }
> >  
> >  static const struct dw_hdmi_plat_data rcar_dw_hdmi_plat_data = {
> > +	.mode_valid = rcar_hdmi_mode_valid,
> >  	.configure_phy	= rcar_hdmi_phy_configure,
> >  };

-- 
Regards,

Laurent Pinchart