Re: [PATCH 7/5] drm/i915: Improve gen3/4 frame counter

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

On Tue, Feb 18, 2014 at 04:16:00PM +0200, Imre Deak wrote:
> On Tue, 2014-02-18 at 14:04 +0200, ville.syrjala@linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > 
> > Currently the logic to fix up the frame counter on gen3/4 assumes that
> > start of vblank occurs at vblank_start*htotal pixels, when in fact
> > it occurs htotal-hsync_start pixels earlier. Apply the appropriate
> > adjustment to make the frame counter more accurate.
> > 
> > Also fix the vblank start position for interlaced display modes.
> > 
> > Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > ---
> >  drivers/gpu/drm/i915/i915_irq.c | 21 ++++++++++++++++-----
> >  1 file changed, 16 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index 9f1c449..fc49fb6 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -639,7 +639,7 @@ static u32 i915_get_vblank_counter(struct drm_device *dev, int pipe)
> >  	drm_i915_private_t *dev_priv = (drm_i915_private_t *) dev->dev_private;
> >  	unsigned long high_frame;
> >  	unsigned long low_frame;
> > -	u32 high1, high2, low, pixel, vbl_start;
> > +	u32 high1, high2, low, pixel, vbl_start, hsync_start, htotal;
> >  
> >  	if (!i915_pipe_enabled(dev, pipe)) {
> >  		DRM_DEBUG_DRIVER("trying to get vblank count for disabled "
> > @@ -653,17 +653,28 @@ static u32 i915_get_vblank_counter(struct drm_device *dev, int pipe)
> >  		const struct drm_display_mode *mode =
> >  			&intel_crtc->config.adjusted_mode;
> >  
> > -		vbl_start = mode->crtc_vblank_start * mode->crtc_htotal;
> > +		htotal = mode->crtc_htotal;
> > +		hsync_start = mode->crtc_hsync_start;
> > +		vbl_start = mode->crtc_vblank_start;
> > +		if (mode->flags & DRM_MODE_FLAG_INTERLACE)
> > +			vbl_start = DIV_ROUND_UP(vbl_start, 2);
> 
> The adjustment for interlace mode is already done in drm_mode_setcrtc,
> so I think we don't need it here.

We throw away the values filled in by drm_mode_setcrtc(). Which is a
good thing since it rounds the result the wrong way (for our hardware
at least). The values we see here are filled in by
intel_modeset_pipe_config() which doesn't pass the
CRTC_INTERLACE_HALVE_V flag to drm_mode_set_crtcinfo().

> Otherwise this patch makes sense to me
> based on the signal chart you drew on this, so:
> 
> Reviewed-by: Imre Deak <imre.deak@intel.com>
> 
> >  	} else {
> >  		enum transcoder cpu_transcoder = (enum transcoder) pipe;
> > -		u32 htotal;
> >  
> >  		htotal = ((I915_READ(HTOTAL(cpu_transcoder)) >> 16) & 0x1fff) + 1;
> > +		hsync_start = (I915_READ(HSYNC(cpu_transcoder))  & 0x1fff) + 1;
> >  		vbl_start = (I915_READ(VBLANK(cpu_transcoder)) & 0x1fff) + 1;
> > -
> > -		vbl_start *= htotal;
> > +		if ((I915_READ(PIPECONF(cpu_transcoder)) &
> > +		     PIPECONF_INTERLACE_MASK) != PIPECONF_PROGRESSIVE)
> > +			vbl_start = DIV_ROUND_UP(vbl_start, 2);
> >  	}
> >  
> > +	/* Convert to pixel count */
> > +	vbl_start *= htotal;
> > +
> > +	/* Start of vblank event occurs at start of hsync */
> > +	vbl_start -= htotal - hsync_start;
> > +
> >  	high_frame = PIPEFRAME(pipe);
> >  	low_frame = PIPEFRAMEPIXEL(pipe);
> >  
> 



-- 
Ville Syrjälä
Intel OTC