[Intel-gfx] [PATCH 2/2] drm/i915: Parse max HDMI TMDS clock from VBT

[Chris Wilson]

Quoting Ville Syrjälä (2017-10-26 16:51:23)
> On Thu, Oct 26, 2017 at 04:44:39PM +0100, Chris Wilson wrote:
> > Quoting Ville Syrjala (2017-10-26 16:14:05)
> > > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > 
> > > Starting from version 204 VBT can specify the max TMDS clock we are
> > > allowed to use with HDMI ports. Parse that information and take it
> > > into account when filtering modes and computing a crtc state.
> > >  
> > > +       if (bdb_version >= 204) {
> > > +               int max_tmds_clock;
> > > +
> > > +               switch (child->hdmi_max_data_rate) {
> > > +               case 1:
> > > +                       max_tmds_clock = 297000;
> > > +                       break;
> > > +               case 2:
> > > +                       max_tmds_clock = 165000;
> > > +                       break;
> > > +               default:
> > > +                       max_tmds_clock = 0;
> > 
> > Is zero a valid value, as this will prevent us from using the output
> > at all?
> 
> Zero means "unlimited" or "use the platform default maximum". The code
> using this will check to make sure it's non-zero before doing the min().

Indeed, I didn't look at the guard closely enough, just expected it to
be a if (use_vbt_flag) and not if (max_tmds_clock).
-Chris