Re: [PATCH] drm/i915/gen9: Check for DC state mismatch

["Vivi, Rodrigo" <rodrigo.vivi@intel.com>]

I was going to merge here but I saw on patchwork we got some warnings
so I'm not sure they are only false positives or this is exactly what
this patches wants...

On Thu, 2016-02-11 at 12:43 +0200, Mika Kuoppala wrote:
> Patrik Jakobsson <patrik.jakobsson@linux.intel.com> writes:
> 
> > The DMC can incorrectly run off and allow DC states on it's own. We
> > don't know the root-cause for this yet but this patch makes it more
> > visible.
> > 
> > Signed-off-by: Patrik Jakobsson <patrik.jakobsson@linux.intel.com>
> 
> Yes, we definitely need much more state checking and hardening
> in this area.
> 
> Reviewed-by: Mika Kuoppala <mika.kuoppala@intel.com>
> 
> 
> > ---
> >  drivers/gpu/drm/i915/i915_drv.h         | 1 +
> >  drivers/gpu/drm/i915/intel_csr.c        | 2 ++
> >  drivers/gpu/drm/i915/intel_runtime_pm.c | 8 ++++++++
> >  3 files changed, 11 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h 
> > b/drivers/gpu/drm/i915/i915_drv.h
> > index e11eef1..7e33454 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -746,6 +746,7 @@ struct intel_csr {
> >  	uint32_t mmio_count;
> >  	i915_reg_t mmioaddr[8];
> >  	uint32_t mmiodata[8];
> > +	uint32_t dc_state;
> >  };
> >  
> >  #define DEV_INFO_FOR_EACH_FLAG(func, sep) \
> > diff --git a/drivers/gpu/drm/i915/intel_csr.c 
> > b/drivers/gpu/drm/i915/intel_csr.c
> > index 2a7ec31..b453fcc 100644
> > --- a/drivers/gpu/drm/i915/intel_csr.c
> > +++ b/drivers/gpu/drm/i915/intel_csr.c
> > @@ -243,6 +243,8 @@ void intel_csr_load_program(struct 
> > drm_i915_private *dev_priv)
> >  		I915_WRITE(dev_priv->csr.mmioaddr[i],
> >  			   dev_priv->csr.mmiodata[i]);
> >  	}
> > +
> > +	dev_priv->csr.dc_state = 0;
> >  }
> >  
> >  static uint32_t *parse_csr_fw(struct drm_i915_private *dev_priv,
> > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c 
> > b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > index bbca527..e79674b 100644
> > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> > @@ -494,10 +494,18 @@ static void gen9_set_dc_state(struct 
> > drm_i915_private *dev_priv, uint32_t state)
> >  	val = I915_READ(DC_STATE_EN);
> >  	DRM_DEBUG_KMS("Setting DC state from %02x to %02x\n",
> >  		      val & mask, state);
> > +
> > +	/* Check if DMC is ignoring our DC state requests */
> > +	if ((val & mask) != dev_priv->csr.dc_state)
> > +		DRM_ERROR("DC state mismatch (0x%x -> 0x%x)\n",
> > +			  dev_priv->csr.dc_state, val & mask);
> > +
> >  	val &= ~mask;
> >  	val |= state;
> >  	I915_WRITE(DC_STATE_EN, val);
> >  	POSTING_READ(DC_STATE_EN);
> > +
> > +	dev_priv->csr.dc_state = val & mask;
> >  }
> >  
> >  void bxt_enable_dc9(struct drm_i915_private *dev_priv)
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