Comment # 46 on bug 76564 from jeroen

(In reply to comment #45)
> (In reply to comment #44)
> > (In reply to comment #43)
> > > We could also update the adjusted mode clock to the actual clock set by the
> > > pll so that drm_calc_timestamping_constants() uses the actual clock value on
> > > the PLL.  E.g.,
> > > 
> > > diff --git a/drivers/gpu/drm/radeon/atombios_crtc.c
> > > b/drivers/gpu/drm/radeon/atombios_crtc.c
> > > index daa4dd3..2a2da82 100644
> > > --- a/drivers/gpu/drm/radeon/atombios_crtc.c
> > > +++ b/drivers/gpu/drm/radeon/atombios_crtc.c
> > > @@ -1085,6 +1085,7 @@ static void atombios_crtc_set_pll(struct drm_crtc
> > > *crtc, struct drm_display_mode
> > >                 atombios_crtc_program_ss(rdev, ATOM_ENABLE,
> > > radeon_crtc->pll_id,
> > >                                          radeon_crtc->crtc_id,
> > > &radeon_crtc->ss);
> > >         }
> > > +       mode->clock = pll_clock * 10;
> > >  }
> > >  
> > >  static int dce4_crtc_do_set_base(struct drm_crtc *crtc,
> > 
> > I think that would only help if radeon_compute_pll_avivo could not compute
> > an exact match. In the case of 23.976Hz the target clock is 74170kHz and the
> > PLL is set exactly to this value.
> > This does raise another question why the target clock' last digit is always
> > zero? For example, for 23.976Hz the target clock should be 74176kHz (with
> > correct rounding). I looked through the source code, but the target clock
> > seems to come all the way from some deep generic drm code.
> > 
> > 74176kHz could be matched by the PLL using fb=927.2, post_div=10 and
> > ref_div=125
> 
> You might want to take a look at atombios_adjust_pll which does the mode
> fixup before a mode is actually used.
> 
> Since atombios always works with 10khz pixel clock which always sets the
> target clocks last digit to zero.

atombios_adjust_pll seems to do nothing to compensate for the 10kHz pixel
clock, or didn't you mean that?

When I look at drm_calc_timestamping_constants(), does this mean the vblank
moment is calculated by the OSS driver?

What about Alex' idea in comment 43? Would tat help Christian?