Re: [PATCH 07/21] drm/i915: Allow enable/disable of DPLL0 around cdclk changes on SKL

[Imre Deak <imre.deak@intel.com>]

On to, 2016-05-19 at 16:18 +0300, Ville Syrjälä wrote:
> On Thu, May 19, 2016 at 04:04:40PM +0300, Imre Deak wrote:
> > On pe, 2016-05-13 at 23:41 +0300, ville.syrjala@linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > In case we originally guessed wrong which lcpll vco frequency to use,
> > > we will need to shut down the pll and restart it when reprogamming the
> > > cdclk.
> > > 
> > > This also allows us to track the actual vco frequency in dev_priv
> > > instead of just a guess.
> > > 
> > > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 54 +++++++++++++++++++-----------------
> > >  1 file changed, 29 insertions(+), 25 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index 95997eed9dd6..cd2809179042 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -5626,6 +5626,8 @@ skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
> > >  
> > >  	if (wait_for(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK, 5))
> > >  		DRM_ERROR("DPLL0 not locked\n");
> > > +
> > > +	dev_priv->skl_vco_freq = vco;
> > >  }
> > >  
> > >  static void
> > > @@ -5634,6 +5636,8 @@ skl_dpll0_disable(struct drm_i915_private *dev_priv)
> > >  	I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) & ~LCPLL_PLL_ENABLE);
> > >  	if (wait_for(!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK), 1))
> > >  		DRM_ERROR("Couldn't disable DPLL0\n");
> > > +
> > > +	dev_priv->skl_vco_freq = 0;
> > >  }
> > >  
> > >  static bool skl_cdclk_pcu_ready(struct drm_i915_private *dev_priv)
> > > @@ -5663,12 +5667,14 @@ static bool skl_cdclk_wait_for_pcu_ready(struct drm_i915_private *dev_priv)
> > >  	return false;
> > >  }
> > >  
> > > -static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk)
> > > +static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk, int vco)
> > >  {
> > >  	struct drm_device *dev = dev_priv->dev;
> > >  	u32 freq_select, pcu_ack;
> > >  
> > > -	DRM_DEBUG_DRIVER("Changing CDCLK to %dKHz\n", cdclk);
> > > +	WARN_ON((cdclk == 24000) != (vco == 0));
> > > +
> > > +	DRM_DEBUG_DRIVER("Changing CDCLK to %d kHz (VCO %d MHz)\n", cdclk, vco);
> > >  
> > >  	if (!skl_cdclk_wait_for_pcu_ready(dev_priv)) {
> > >  		DRM_ERROR("failed to inform PCU about cdclk change\n");
> > > @@ -5699,6 +5705,13 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk)
> > >  		break;
> > >  	}
> > >  
> > > +	if (dev_priv->skl_vco_freq != 0 &&
> > > +	    dev_priv->skl_vco_freq != vco)
> > > +		skl_dpll0_disable(dev_priv);
> > > +
> > > +	if (dev_priv->skl_vco_freq != vco)
> > > +		skl_dpll0_enable(dev_priv, vco);
> > > +
> > >  	I915_WRITE(CDCLK_CTL, freq_select | skl_cdclk_decimal(cdclk));
> > >  	POSTING_READ(CDCLK_CTL);
> > >  
> > > @@ -5721,26 +5734,21 @@ void skl_uninit_cdclk(struct drm_i915_private *dev_priv)
> > >  	if (I915_READ(DBUF_CTL) & DBUF_POWER_STATE)
> > >  		DRM_ERROR("DBuf power disable timeout\n");
> > >  
> > > -	skl_dpll0_disable(dev_priv);
> > > +	skl_set_cdclk(dev_priv, 24000, 0);
> > 
> > The spec doesn't say how to program CDCLK for the bypass case and we'll
> > program the 'frequency decimal' field to something isn't listed as a
> > valid value (and not matching the CD frequency select value). But I
> > think CDCLK is don't-care in that case, so it's fine.
> > 
> > >  }
> > >  
> > >  void skl_init_cdclk(struct drm_i915_private *dev_priv)
> > >  {
> > > -	unsigned int cdclk;
> > > -
> > >  	/* DPLL0 not enabled (happens on early BIOS versions) */
> > > -	if (!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_ENABLE)) {
> > > -		/* enable DPLL0 */
> > > -		if (dev_priv->skl_vco_freq != 8640)
> > > -			dev_priv->skl_vco_freq = 8100;
> > > -		skl_dpll0_enable(dev_priv, dev_priv->skl_vco_freq);
> > > -		cdclk = skl_calc_cdclk(0, dev_priv->skl_vco_freq);
> > > -	} else {
> > > -		cdclk = dev_priv->cdclk_freq;
> > > -	}
> > > +	if (dev_priv->skl_vco_freq == 0) {
> > > +		int cdclk, vco;
> > >  
> > > -	/* set CDCLK to the lowest frequency, Modeset follows */
> > > -	skl_set_cdclk(dev_priv, cdclk);
> > > +		/* set CDCLK to the lowest frequency, Modeset follows */
> > > +		vco = 8100;
> > > +		cdclk = skl_calc_cdclk(0, vco);
> > > +
> > > +		skl_set_cdclk(dev_priv, cdclk, vco);
> > > +	}
> > >  
> > >  	/* enable DBUF power */
> > >  	I915_WRITE(DBUF_CTL, I915_READ(DBUF_CTL) | DBUF_POWER_REQUEST);
> > > @@ -9777,16 +9785,12 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
> > >  
> > >  static void skl_modeset_commit_cdclk(struct drm_atomic_state *old_state)
> > 
> > Why is the above called old_state?
> 
> Because atomic is stupid. There's just one top level state which starts
> out as the new state, but later we swap the connector/crtc/plane state
> pointers around so that the top level state points to the old state
> for those things. That's why it's called old_state here. Everything
> else stored in that top level state is not swapped though so it's
> actually an extremely confusing mix of old and new state.

Ok, separating old and new states better would make sense.

> I think what we should do is pull all the state stored in the top level
> atomic state structure into a separate structure and store a pointer to
> that in the top level atomic state just like for everything else. We
> can then swap that pointer as well. That way all the old vs. new stuff
> would be consistent. It migth also clean up the horrible mess with the
> atomic_cdclk stuff and whatnot.

On that note AFAICS dev_priv->atomic_cdclk_freq is just dev_priv-
>cdclk_freq. If so would be good to simplify, if not some code comment
about the real justification for atomic_cdclk_freq would be nice. 

--Imre

> 
> > 
> > The patch looks ok:
> > Reviewed-by: Imre Deak <imre.deak@intel.com>
> > 
> > >  {
> > > -	struct drm_device *dev = old_state->dev;
> > > -	struct drm_i915_private *dev_priv = dev->dev_private;
> > > -	unsigned int req_cdclk = to_intel_atomic_state(old_state)->dev_cdclk;
> > > -
> > > -	/*
> > > -	 * FIXME disable/enable PLL should wrap set_cdclk()
> > > -	 */
> > > -	skl_set_cdclk(dev_priv, req_cdclk);
> > > +	struct drm_i915_private *dev_priv = to_i915(old_state->dev);
> > > +	struct intel_atomic_state *intel_state = to_intel_atomic_state(old_state);
> > > +	unsigned int req_cdclk = intel_state->dev_cdclk;
> > > +	unsigned int req_vco = intel_state->cdclk_pll_vco;
> > >  
> > > -	dev_priv->skl_vco_freq = to_intel_atomic_state(old_state)->cdclk_pll_vco;
> > > +	skl_set_cdclk(dev_priv, req_cdclk, req_vco);
> > >  }
> > >  
> > >  static int haswell_crtc_compute_clock(struct intel_crtc *crtc,
> 
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