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

Ville Syrjälä
2015-02-27T20:48:22Z

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