Re: [Intel-gfx] [V13 5/5] drm/i915/dsi: Enable software vblank counter

["Kulkarni, Vandita" <vandita.kulkarni@intel.com>]

> -----Original Message-----
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Sent: Wednesday, September 23, 2020 3:30 PM
> To: Kulkarni, Vandita <vandita.kulkarni@intel.com>
> Cc: intel-gfx@lists.freedesktop.org; Nikula, Jani <jani.nikula@intel.com>
> Subject: Re: [V13 5/5] drm/i915/dsi: Enable software vblank counter
> 
> On Tue, Sep 22, 2020 at 07:14:26PM +0530, Vandita Kulkarni wrote:
> > In case of DSI cmd mode, we get hw vblank counter updated after the TE
> > comes in, if we try to read the hw vblank counter in te handler we
> > wouldnt have the udpated vblank counter yet.
> > This will lead to a state where we would send the vblank event to the
> > user space in the next te, though the frame update would have
> > completed in the first TE duration itself.
> > Hence switch to using software timestamp based vblank counter.
> >
> > Signed-off-by: Vandita Kulkarni <vandita.kulkarni@intel.com>
> > ---
> >  drivers/gpu/drm/i915/display/intel_display.c | 11 +++++++++++
> >  drivers/gpu/drm/i915/i915_irq.c              |  4 ++++
> >  2 files changed, 15 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> > b/drivers/gpu/drm/i915/display/intel_display.c
> > index c4f331f2af45..8b9e59e52708 100644
> > --- a/drivers/gpu/drm/i915/display/intel_display.c
> > +++ b/drivers/gpu/drm/i915/display/intel_display.c
> > @@ -1808,6 +1808,17 @@ enum pipe intel_crtc_pch_transcoder(struct
> > intel_crtc *crtc)  static u32 intel_crtc_max_vblank_count(const struct
> > intel_crtc_state *crtc_state)  {
> >  	struct drm_i915_private *dev_priv =
> > to_i915(crtc_state->uapi.crtc->dev);
> > +	struct intel_crtc *crtc = to_intel_crtc(crtc_state->uapi.crtc);
> > +	u32 flags = crtc->mode_flags;
> 
> That's wrong. You need to look at the crtc_state instead.

Thanks,
I will use crtc_state.

I saw this happening 
crtc->mode_flags = crtc_state->mode_flags;
at intel_crtc_update_active_timings.

Thanks,
-Vandita
> 
> > +
> > +	/*
> > +	 * From Gen 11, In case of dsi cmd mode, frame counter wouldnt
> > +	 * have updated at the beginning of TE, if we want to use
> > +	 * the hw counter, then we would find it updated in only
> > +	 * the next TE, hence switching to sw counter.
> > +	 */
> > +	if (flags & (I915_MODE_FLAG_DSI_USE_TE0 |
> I915_MODE_FLAG_DSI_USE_TE1))
> > +		return 0;
> >
> >  	/*
> >  	 * On i965gm the hardware frame counter reads diff --git
> > a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index c2e4b227bdf3..634c60befe7e 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -682,8 +682,12 @@ u32 i915_get_vblank_counter(struct drm_crtc
> > *crtc)
> >  u32 g4x_get_vblank_counter(struct drm_crtc *crtc)  {
> >  	struct drm_i915_private *dev_priv = to_i915(crtc->dev);
> > +	struct drm_vblank_crtc *vblank =
> > +&dev_priv->drm.vblank[drm_crtc_index(crtc)];
> >  	enum pipe pipe = to_intel_crtc(crtc)->pipe;
> >
> > +	if (!vblank->max_vblank_count)
> > +		return 0;
> > +
> >  	return I915_READ(PIPE_FRMCOUNT_G4X(pipe));
> >  }
> >
> > --
> > 2.21.0.5.gaeb582a
> 
> --
> Ville Syrjälä
> Intel
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