Re: [PATCH 15/26] drm/i915: add media well to VLV force wake routines

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

On Wed, Mar 06, 2013 at 10:33:34AM -0800, Jesse Barnes wrote:
> On Wed, 6 Mar 2013 20:28:07 +0200
> Ville Syrjälä <ville.syrjala@linux.intel.com> wrote:
> 
> > On Fri, Mar 01, 2013 at 02:08:31PM -0800, Jesse Barnes wrote:
> > > We could split this out into a separate routine at some point as an
> > > optimization.
> > 
> > BTW did anyone try to gang wakeup thing instead?
> 
> Not afaik.
> 
> > 
> > > 
> > > Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> > > ---
> > >  drivers/gpu/drm/i915/i915_reg.h |    2 ++
> > >  drivers/gpu/drm/i915/intel_pm.c |   11 ++++++++---
> > >  2 files changed, 10 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> > > index 1c6e066..558c6d1 100644
> > > --- a/drivers/gpu/drm/i915/i915_reg.h
> > > +++ b/drivers/gpu/drm/i915/i915_reg.h
> > > @@ -4271,6 +4271,8 @@
> > >  #define  FORCEWAKE				0xA18C
> > >  #define  FORCEWAKE_VLV				0x1300b0
> > >  #define  FORCEWAKE_ACK_VLV			0x1300b4
> > > +#define  FORCEWAKE_MEDIA_VLV			0x1300b8
> > > +#define  FORCEWAKE_ACK_MEDIA_VLV		0x1300bc
> > >  #define  FORCEWAKE_ACK_HSW			0x130044
> > >  #define  FORCEWAKE_ACK				0x130090
> > >  #define  VLV_GTLC_WAKE_CTRL			0x130090
> > > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > > index 3e976f4..e3947cb 100644
> > > --- a/drivers/gpu/drm/i915/intel_pm.c
> > > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > > @@ -4423,10 +4423,15 @@ static void vlv_force_wake_get(struct drm_i915_private *dev_priv)
> > >  		DRM_ERROR("Timed out waiting for forcewake old ack to clear.\n");
> > >  
> > >  	I915_WRITE_NOTRACE(FORCEWAKE_VLV, _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
> > > +	I915_WRITE_NOTRACE(FORCEWAKE_MEDIA_VLV, _MASKED_BIT_ENABLE(FORCEWAKE_KERNEL));
> > >  
> > >  	if (wait_for_atomic((I915_READ_NOTRACE(FORCEWAKE_ACK_VLV) & 1),
> > >  			    FORCEWAKE_ACK_TIMEOUT_MS))
> > > -		DRM_ERROR("Timed out waiting for forcewake to ack request.\n");
> > > +		DRM_ERROR("Timed out waiting for GT to ack forcewake request.\n");
> > > +
> > > +	if (wait_for_atomic((I915_READ_NOTRACE(FORCEWAKE_ACK_MEDIA_VLV) & 1),
> > > +			    FORCEWAKE_ACK_TIMEOUT_MS))
> > > +		DRM_ERROR("Timed out waiting for media to ack forcewake request.\n");
> > 
> > Based on some of my recent patches the '& 1's should be
> > '& FORCEWAKE_KERNEL'.
> 
> And that was based on my misunderstanding of MT forcewake.  I thought
> it was so the BIOS or AMT could do forcewake, but it's actually meant
> for multiple kernel thread accesses.  Since we don't do that, simply
> using the lowest bit all the time is fine.

I just want to be consistent which names we give the bits to avoid
confusing people (mainly myself), that's all.

> > >  	__gen6_gt_wait_for_thread_c0(dev_priv);
> > >  }
> > > @@ -4434,8 +4439,8 @@ static void vlv_force_wake_get(struct drm_i915_private *dev_priv)
> > >  static void vlv_force_wake_put(struct drm_i915_private *dev_priv)
> > >  {
> > >  	I915_WRITE_NOTRACE(FORCEWAKE_VLV, _MASKED_BIT_DISABLE(FORCEWAKE_KERNEL));
> > > -	/* something from same cacheline, but !FORCEWAKE_VLV */
> > > -	POSTING_READ(FORCEWAKE_ACK_VLV);
> > > +	I915_WRITE_NOTRACE(FORCEWAKE_MEDIA_VLV, _MASKED_BIT_DISABLE(FORCEWAKE_KERNEL));
> > > +	/* The below doubles as a POSTING_READ */
> > 
> > Are we sure? ;)
> > 
> > >  	gen6_gt_check_fifodbg(dev_priv);
> 
> Well it does a read first thing so I think so.

But does it read the right magic register? Referring to the magic ECOBUS
mess we had earlier. But if this code actually works, then I guess we
can be happy.

-- 
Ville Syrjälä
Intel OTC