[Intel-gfx] [PATCH 1/2] drm/i915: Use same DPLL calculation logic to calculate the LVDS downclock and normal clock

[ykzhao]

On Mon, 2009-12-21 at 08:55 +0800, ykzhao wrote:
> On Tue, 2009-12-15 at 21:13 +0800, Zhao, Yakui wrote:
> > From: Zhao Yakui <yakui.zhao at intel.com>
> > 
> Hi, Eric
>     Any comment about this patch?

Hi, Eric
   Any comment about this patch?

Thanks.
   Yakui
>     
> thanks.
>     Yakui
> > Now when the reduced downclock is found for LVDS, we will use find_reduced_pll
> > callback function to calculate the corresponding DPLL parameter(M/N/P)for
> > reduced downclock. In this function we will use the dividor factor(P) obtained 
> > for the normal clock to calculate the DPLL parameter(M/N). It is not
> > appropriate.
> > 
> > According to the spec only one M/N/P combination is appropriate for one given
> > clock regardless of normal clock or reduced downclock. This M/N/P combination
> > is defined in one spreadsheet(Of course our code uses the find_pll callback
> > function to calculate the M/N/P instead of looking up it in table). In theory
> > we should get the same DPLL divider factor(P) for the normal clock and reduced
> > downclock when the LVDS reduced downclock is found on one laptop.
> > If we get the diferent divider factor(P) for normal clock and reduced
> > clock, the reduced downclock is incorrect and should be discarded.
> > 
> > So we should use find_pll callback to calculate the DPLL parameter for the
> > LVDS reduced downclock as for the normal clock.
> > 
> > Signed-off-by: Zhao Yakui <yakui.zhao at intel.com>
> > cc: Jesse Barnes <jbarnes at virtuousgeek.org>
> > cc: Matthew Garrett <mjg at redhat.com>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c |    6 ++----
> >  1 files changed, 2 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 279dc96..1ad2fd9 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -2906,10 +2906,8 @@ static int intel_crtc_mode_set(struct drm_crtc *crtc,
> >  		return -EINVAL;
> >  	}
> >  
> > -	if (is_lvds && limit->find_reduced_pll &&
> > -			dev_priv->lvds_downclock_avail) {
> > -		memcpy(&reduced_clock, &clock, sizeof(intel_clock_t));
> > -		has_reduced_clock = limit->find_reduced_pll(limit, crtc,
> > +	if (is_lvds && dev_priv->lvds_downclock_avail) {
> > +		has_reduced_clock = limit->find_pll(limit, crtc,
> >  							    dev_priv->lvds_downclock,
> >  							    refclk,
> >  							    &reduced_clock);
> 
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