[PATCH v2] drm: rcar-du: dw-hdmi: Reject modes with a too high clock frequency

[Geert Uytterhoeven]

Hi Laurent,

On Tue, Dec 4, 2018 at 7:12 PM Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> On Tuesday, 4 December 2018 19:30:25 EET Geert Uytterhoeven wrote:
> > On Tue, Dec 4, 2018 at 5:36 PM 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>
> >
> > Thanks for your patch!
> >
> > > --- a/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> > > +++ b/drivers/gpu/drm/rcar-du/rcar_dw_hdmi.c
> > > @@ -35,6 +35,20 @@ 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)
> > > +{
> > > +       /*
> > > +        * The maximum supported clock frequency is 297 MHz, as shown in
> > > the PHY +        * parameters table.
> > > +        */
> > > +       if (mode->clock > 297000)
> > > +               return MODE_CLOCK_HIGH;
> >
> > Perhaps you need a check for the lower limit (25 MHz), too?
>
> There's no lower limit implied by the rcar_hdmi_phy_params table.

Oh, you mean the table in the driver, not a table in the Hardware User's
Manual?
That's why I couldn't find the table, but only a short notice in the HDMI
section of the Hardware User's Manual, stating:

    Pixel clock from 25MHz up to 297MHz

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds