Re: [PATCH] drm/i915/vlv: add VLV specific clock_get function v3

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Mon, 23 Sep 2013 21:01:44 +0300
Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:

> On Fri, Sep 20, 2013 at 11:29:32AM -0700, Jesse Barnes wrote:
> > Calculation is a little different than other platforms.
> > 
> > v2: update to use port_clock instead
> >     rebase on top of Ville's changes
> > v3: update to new port_clock semantics - don't divide by
> >     pixel_multiplier (Ville)
> > 
> > References: https://bugs.freedesktop.org/show_bug.cgi?id=67345
> > Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c |   33 ++++++++++++++++++++++++++++++++-
> >  1 file changed, 32 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index 7eecf37..e5c9c1c 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -5048,6 +5048,34 @@ static void i9xx_get_pfit_config(struct intel_crtc *crtc,
> >  			I915_READ(LVDS) & LVDS_BORDER_ENABLE;
> >  }
> >  
> > +static void vlv_crtc_clock_get(struct intel_crtc *crtc,
> > +			       struct intel_crtc_config *pipe_config)
> > +{
> > +	struct drm_device *dev = crtc->base.dev;
> > +	struct drm_i915_private *dev_priv = dev->dev_private;
> > +	int pipe = pipe_config->cpu_transcoder;
> > +	intel_clock_t clock;
> > +	u32 mdiv;
> > +	int refclk = 100000, fastclk, update_rate;
> > +
> > +	mutex_lock(&dev_priv->dpio_lock);
> > +	mdiv = vlv_dpio_read(dev_priv, pipe, DPIO_DIV(pipe));
> > +	mutex_unlock(&dev_priv->dpio_lock);
> > +
> > +	clock.m1 = (mdiv >> DPIO_M1DIV_SHIFT) & 7;
> > +	clock.m2 = mdiv & DPIO_M2DIV_MASK;
> > +	clock.n = (mdiv >> DPIO_N_SHIFT) & 0xf;
> > +	clock.p1 = (mdiv >> DPIO_P1_SHIFT) & 7;
> > +	clock.p2 = (mdiv >> DPIO_P2_SHIFT) & 0x1f;
> > +
> > +	update_rate = refclk / clock.n;
> > +	clock.vco = update_rate * clock.m1 * clock.m2;
> > +	fastclk = clock.vco / clock.p1 / clock.p2;
> > +	clock.dot = (2 * fastclk);
> > +
> > +	pipe_config->port_clock = clock.dot / 10;
> 
> Looks like it should get roughly the right answer, but I don't see much
> point in all the intermediate results.
> 
> If you want to keep some of them for clarity, then I think this should
> be enough:
> 
> clock.vco = refclk * clock.m / clock.n;
> clock.dot = clock.vco / clock.p; /* fast clock */
> pipe_config->port_clock = clock.dot / 5;
> 
> Although calling the fast clock "dot" is a bit wrong, but I think it's
> fine here, especially as it matches what I have in mind for
> vlv_find_best_dpll(). I had to rewrite that sucker a bit to make it
> compatible with my brain ;) I'll send a patch for that ASAP.

The other advantage of having it all spelled out like this is that it
matches the freq calculation spreadsheet I sourced it from.

So I'd prefer to keep this as is, if I can have your r-b anyway. :)

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center
_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
http://lists.freedesktop.org/mailman/listinfo/intel-gfx