[Intel-gfx] [PATCH 04/19] drm/i915: Add support for detecting vblanks when hw frame counter is unavailable.

[Patrik Jakobsson]

On Wed, Apr 27, 2016 at 05:23:06PM +0300, Ville Syrjälä wrote:
> On Wed, Apr 27, 2016 at 04:06:16PM +0200, Patrik Jakobsson wrote:
> > On Tue, Apr 19, 2016 at 09:52:24AM +0200, Maarten Lankhorst wrote:
> > > This uses the newly created drm_accurate_vblank_count_and_time to accurately
> > > get a vblank count when the hw counter is unavailable.
> > > ---
> > >  drivers/gpu/drm/i915/intel_display.c | 10 ++++++++++
> > >  drivers/gpu/drm/i915/intel_drv.h     |  3 +++
> > >  drivers/gpu/drm/i915/intel_sprite.c  |  8 ++------
> > >  3 files changed, 15 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > > index ccbc2a448258..2086e8bd10da 100644
> > > --- a/drivers/gpu/drm/i915/intel_display.c
> > > +++ b/drivers/gpu/drm/i915/intel_display.c
> > > @@ -13530,6 +13530,16 @@ static int intel_atomic_prepare_commit(struct drm_device *dev,
> > >  	return ret;
> > >  }
> > >  
> > > +u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc)
> > > +{
> > > +	struct drm_device *dev = crtc->base.dev;
> > > +
> > > +	if (!dev->max_vblank_count)
> > > +		return drm_accurate_vblank_count(&crtc->base);
> > > +
> > > +	return dev->driver->get_vblank_counter(dev, crtc->pipe);
> > > +}
> > > +
> > >  static void intel_atomic_wait_for_vblanks(struct drm_device *dev,
> > >  					  struct drm_i915_private *dev_priv,
> > >  					  unsigned crtc_mask)
> > > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > > index fecc89600667..8efeb90eac07 100644
> > > --- a/drivers/gpu/drm/i915/intel_drv.h
> > > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > > @@ -1146,6 +1146,9 @@ intel_wait_for_vblank_if_active(struct drm_device *dev, int pipe)
> > >  	if (crtc->active)
> > >  		intel_wait_for_vblank(dev, pipe);
> > >  }
> > > +
> > > +u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc);
> > > +
> > >  int ironlake_get_lanes_required(int target_clock, int link_bw, int bpp);
> > >  void vlv_wait_port_ready(struct drm_i915_private *dev_priv,
> > >  			 struct intel_digital_port *dport,
> > > diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
> > > index 0f3e2303e0e9..e2de6b0df5a8 100644
> > > --- a/drivers/gpu/drm/i915/intel_sprite.c
> > > +++ b/drivers/gpu/drm/i915/intel_sprite.c
> > > @@ -80,9 +80,7 @@ static int usecs_to_scanlines(const struct drm_display_mode *adjusted_mode,
> > >   */
> > >  void intel_pipe_update_start(struct intel_crtc *crtc)
> > >  {
> > > -	struct drm_device *dev = crtc->base.dev;
> > >  	const struct drm_display_mode *adjusted_mode = &crtc->config->base.adjusted_mode;
> > > -	enum pipe pipe = crtc->pipe;
> > >  	long timeout = msecs_to_jiffies_timeout(1);
> > >  	int scanline, min, max, vblank_start;
> > >  	wait_queue_head_t *wq = drm_crtc_vblank_waitqueue(&crtc->base);
> > > @@ -139,8 +137,7 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
> > >  
> > >  	crtc->debug.scanline_start = scanline;
> > >  	crtc->debug.start_vbl_time = ktime_get();
> > > -	crtc->debug.start_vbl_count =
> > > -		dev->driver->get_vblank_counter(dev, pipe);
> > > +	crtc->debug.start_vbl_count = intel_crtc_get_vblank_counter(crtc);
> > >  
> > >  	trace_i915_pipe_update_vblank_evaded(crtc);
> > >  }
> > > @@ -156,10 +153,9 @@ void intel_pipe_update_start(struct intel_crtc *crtc)
> > >   */
> > >  void intel_pipe_update_end(struct intel_crtc *crtc)
> > >  {
> > > -	struct drm_device *dev = crtc->base.dev;
> > >  	enum pipe pipe = crtc->pipe;
> > >  	int scanline_end = intel_get_crtc_scanline(crtc);
> > > -	u32 end_vbl_count = dev->driver->get_vblank_counter(dev, pipe);
> > > +	u32 end_vbl_count = intel_crtc_get_vblank_counter(crtc);
> > >  	ktime_t end_vbl_time = ktime_get();
> > >  
> > >  	trace_i915_pipe_update_end(crtc, end_vbl_count, scanline_end);
> > 
> > Do we need to use intel_crtc_get_vblank_counter() in
> > display_pipe_crc_irq_handler() as well?
> 
> There was a bit of talk whether we should use hw or sw counter for the
> crc frame numbers, but I can't remember if we reached any real
> conclusion. In the meantime the crc frame counters are all still zero
> on gen2, meaning the tests don't work all that well. See [1].
> 
> And we still have the %8d bug highlited in that same patch series. Not
> sure we reached any conclusion about that on either.
> 
> In any case using drm_accurate_vblank_count() from the irq handler
> would be somewhat silly since the irq handler should have just updated
> the sw counter to be uptodate, assuming we had vblank irqs enabled.
> 
> [1] https://lists.freedesktop.org/archives/intel-gfx/2015-December/083035.html

Ok, let's leave it as it is for now.

Reviewed-by: Patrik Jakobsson <patrik.jakobsson at linux.intel.com>

> 
> -- 
> Ville Syrjälä
> Intel OTC
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