Re: [PATCH] drm/i915: Avoid vblank counter for gen9+

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

On Fri, 2016-02-12 at 11:34 +0200, David Weinehall wrote:
> On Thu, Feb 11, 2016 at 09:00:47AM -0800, Rodrigo Vivi wrote:
> > Framecounter register is read-only so DMC cannot restore it
> > after exiting DC5 and DC6.
> > 
> > Easiest way to go is to avoid the counter and use vblank
> > interruptions for this platform and for all the following
> > ones since DMC came to stay. At least while we can't change
> > this register to read-write.
> > 
> > Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_irq.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c 
> > b/drivers/gpu/drm/i915/i915_irq.c
> > index 25a8937..c294a4b 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -4556,7 +4556,10 @@ void intel_irq_init(struct drm_i915_private 
> > *dev_priv)
> >  
> >  	pm_qos_add_request(&dev_priv->pm_qos, 
> > PM_QOS_CPU_DMA_LATENCY, PM_QOS_DEFAULT_VALUE);
> >  
> > -	if (IS_GEN2(dev_priv)) {
> > +	if (INTEL_INFO(dev_priv)->gen >= 9) {
> > +		dev->max_vblank_count = 0;
> > +		dev->driver->get_vblank_counter = 
> > g4x_get_vblank_counter;
> > +	} else if (IS_GEN2(dev_priv)) {
> >  		dev->max_vblank_count = 0;
> >  		dev->driver->get_vblank_counter = 
> > i8xx_get_vblank_counter;
> >  	} else if (IS_G4X(dev_priv) || INTEL_INFO(dev_priv)->gen 
> > >= 5) {
> > @@ -4572,7 +4575,7 @@ void intel_irq_init(struct drm_i915_private 
> > *dev_priv)
> >  	 * Gen2 doesn't have a hardware frame counter and so 
> > depends on
> >  	 * vblank interrupts to produce sane vblank seuquence 
> > numbers.
> >  	 */
> > -	if (!IS_GEN2(dev_priv))
> > +	if (!IS_GEN2(dev_priv) && !INTEL_INFO(dev_priv)->gen >= 9)
> 
> I think this should be:
> 
> if (INTEL_INFO(dev_priv)->gen < 9)

Yeap, < 9 is better...

> 
> If gen < 9, then IS_GEN2 is always true, also ! has higher precedence
> than >=, so you're essentially comparing whether the logical negation 
> of
> INTEL_INFO(dev_priv)->gen is >= 9.

but it is also !gen2

So I believe the right is

if (INTEL_INFO(dev_priv)->gen < 9 && !IS_GEN2(dev_priv))

agree?

> 
> 
> Kind regards, David
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