Re: [PATCH 08/12] drm/i915: Make sure PND deadline mode is enabled on VLV/CHV

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Fri, Feb 27, 2015 at 12:38:44PM -0800, Jesse Barnes wrote:
> On 02/10/2015 05:28 AM, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Poke at the CBR1_VLV register during init_clock_gating to make sure the
> > PND deadline scheme is used.
> > 
> > The hardware has two modes of operation wrt. watermarks:
> > 
> > 1) PND deadline mode:
> >  - memory request deadline is calculated from actual FIFO level * DDL
> >  - WM1 watermark values are unused (AFAIK)
> >  - WM watermark level defines when to start fetching data from memory
> >    (assuming trickle feed is not used)
> > 
> > 2) backup mode
> >  - deadline is based on FIFO status, DDL is unused
> >  - FIFO split into three regions with WM and WM1 watermarks, each
> >    part specifying a different FIFO status
> > 
> > We want to use the PND deadline mode, so let's make sure the chicken
> > bit is in the correct position on init.
> > 
> > Also take the opportunity to refactor the shared code between VLV and
> > CHV to a shared function.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_reg.h |  3 +++
> >  drivers/gpu/drm/i915/intel_pm.c | 19 +++++++++++++------
> >  2 files changed, 16 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > index 433d7e7..5d377df 100644
> > --- a/drivers/gpu/drm/i915/i915_reg.h
> > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > @@ -4177,6 +4177,9 @@ enum skl_disp_power_wells {
> >  #define DDL_PRECISION_LOW		(0<<7)
> >  #define DRAIN_LATENCY_MASK		0x7f
> >  
> > +#define CBR1_VLV			(VLV_DISPLAY_BASE + 0x70400)
> > +#define  CBR_PND_DEADLINE_DISABLE	(1<<31)
> > +
> >  /* FIFO watermark sizes etc */
> >  #define G4X_FIFO_LINE_SIZE	64
> >  #define I915_FIFO_LINE_SIZE	64
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index e53038e..c021e92 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -6197,11 +6197,22 @@ static void ivybridge_init_clock_gating(struct drm_device *dev)
> >  	gen6_check_mch_setup(dev);
> >  }
> >  
> > +static void vlv_init_display_clock_gating(struct drm_i915_private *dev_priv)
> > +{
> > +	I915_WRITE(DSPCLK_GATE_D, VRHUNIT_CLOCK_GATE_DISABLE);
> > +
> > +	/*
> > +	 * Disable trickle feed and enable pnd deadline calculation
> > +	 */
> > +	I915_WRITE(MI_ARB_VLV, MI_ARB_DISPLAY_TRICKLE_FEED_DISABLE);
> > +	I915_WRITE(CBR1_VLV, 0);
> > +}
> > +
> >  static void valleyview_init_clock_gating(struct drm_device *dev)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  
> > -	I915_WRITE(DSPCLK_GATE_D, VRHUNIT_CLOCK_GATE_DISABLE);
> > +	vlv_init_display_clock_gating(dev_priv);
> >  
> >  	/* WaDisableEarlyCull:vlv */
> >  	I915_WRITE(_3D_CHICKEN3,
> > @@ -6249,8 +6260,6 @@ static void valleyview_init_clock_gating(struct drm_device *dev)
> >  	I915_WRITE(GEN7_UCGCTL4,
> >  		   I915_READ(GEN7_UCGCTL4) | GEN7_L3BANK2X_CLOCK_GATE_DISABLE);
> >  
> > -	I915_WRITE(MI_ARB_VLV, MI_ARB_DISPLAY_TRICKLE_FEED_DISABLE);
> > -
> >  	/*
> >  	 * BSpec says this must be set, even though
> >  	 * WaDisable4x2SubspanOptimization isn't listed for VLV.
> > @@ -6287,9 +6296,7 @@ static void cherryview_init_clock_gating(struct drm_device *dev)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  
> > -	I915_WRITE(DSPCLK_GATE_D, VRHUNIT_CLOCK_GATE_DISABLE);
> > -
> > -	I915_WRITE(MI_ARB_VLV, MI_ARB_DISPLAY_TRICKLE_FEED_DISABLE);
> > +	vlv_init_display_clock_gating(dev_priv);
> >  
> >  	/* WaVSRefCountFullforceMissDisable:chv */
> >  	/* WaDSRefCountFullforceMissDisable:chv */
> > 
> 
> Is the deadline mode preference documented somewhere?  Do we need
> another bspec bug filed?

VLV display cluster HAS had a fairly good description. We can at least
hope it works well enough on VLV. Sadly it doesn't actually work the
way you'd expect on CHV, but that's a whole other story.

> 
> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

-- 
Ville Syrjälä
Intel OTC
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