[Intel-gfx] [PATCH 2/3] drm/i915: Bring UP Power Wells before disabling RC6.

[Daniel Vetter]

On Mon, Dec 09, 2013 at 02:14:03PM +0000, S, Deepak wrote:
> >What precisely does this fix? All our register access is already wrapped in get/put calls, so I'm a bit confused ... Is this to work around hw issues, or is this what the bios expects when going into suspend?
> 
> Yes Daniel, this was sequence recommended when going into suspend/Resume path.

So the BIOS falls over if we don't do this? In that case I think we need
to reword the code comment to say that we're doing this for the BIOS.
Otherwise someone will remove this again, since our own code surely
doesn't need it.
-Daniel

> 
> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch] On Behalf Of Daniel Vetter
> Sent: Monday, December 9, 2013 1:31 PM
> To: S, Deepak
> Cc: intel-gfx at lists.freedesktop.org
> Subject: Re: [Intel-gfx] [PATCH 2/3] drm/i915: Bring UP Power Wells before disabling RC6.
> 
> On Sun, Dec 08, 2013 at 01:52:46PM +0530, deepak.s at intel.com wrote:
> > From: Deepak S <deepak.s at intel.com>
> > 
> > Instead of waiting for HW to bringup the wells, We force the wells up 
> > before disabling RC6. This is to avoid any register access when wells 
> > are down.
> > 
> > Signed-off-by: Deepak S <deepak.s at intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c 
> > b/drivers/gpu/drm/i915/intel_pm.c index 2e1340f..089712a 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -3661,6 +3661,12 @@ static void gen6_disable_rps(struct drm_device 
> > *dev)  static void valleyview_disable_rps(struct drm_device *dev)  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > +	unsigned long irqflags;
> > +
> > +	/* We need to bring up the wells before disabling the RC6 */
> > +	spin_lock_irqsave(&dev_priv->uncore.lock, irqflags);
> > +	dev_priv->uncore.funcs.force_wake_get(dev_priv, FORCEWAKE_ALL);
> > +	spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags);
> 
> What precisely does this fix? All our register access is already wrapped in get/put calls, so I'm a bit confused ... Is this to work around hw issues, or is this what the bios expects when going into suspend?
> -Daniel
> >  
> >  	I915_WRITE(GEN6_RC_CONTROL, 0);
> >  
> > --
> > 1.8.4.2
> > 
> > _______________________________________________
> > Intel-gfx mailing list
> > Intel-gfx at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/intel-gfx
> 
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch