Re: [PATCH] drm/i915: Fix legacy cursor vs. watermarks for ILK-BDW

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Mon, Feb 20, 2017 at 10:04:06AM +0100, Maarten Lankhorst wrote:
> Op 17-02-17 om 16:01 schreef ville.syrjala@xxxxxxxxxxxxxxx:
> > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >
> > In order to make cursor updates actually safe wrt. watermark programming
> > we have to clear the legacy_cursor_update flag in the atomic state. That
> > will cause the regular atomic update path to do the necessary vblank
> > wait after the plane update if needed, otherwise the vblank wait would
> > be skipped and we'd feed the optimal watermarks to the hardware before
> > the plane update has actually happened.
> >
> > To make the slow vs. fast path determination in
> > intel_legacy_cursor_update() a little simpler we can ignore the actual
> > visibility of the plane (which can only get computed once we've already
> > chosen out path) and instead we simply check whether the fb is being
> > set or cleared by the user. This means a fully clipped but logically
> > visible cursor will be considered visible as far as watermark
> > programming is concerned. We can do that for the cursor since it's a
> > fixed size plane and the clipped size doesn't play a role in the
> > watermark computation.
> >
> > This should fix underruns that can occur when the cursor gets
> > enable/disabled or the size gets changed. Hopefully it's good enough
> > that only pure cursor movement and flips go through unthrottled.
> >
> > Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> > Cc: Uwe Kleine-König <uwe@xxxxxxxxxxxxxxxxx>
> > Reported-by: Uwe Kleine-König <uwe@xxxxxxxxxxxxxxxxx>
> > Fixes: f79f26921ee1 ("drm/i915: Add a cursor hack to allow converting legacy page flip to atomic, v3.")
> > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > ---
> >  drivers/gpu/drm/i915/intel_display.c | 29 ++++++++++++++++++-----------
> >  drivers/gpu/drm/i915/intel_pm.c      | 20 ++++++++++++--------
> >  2 files changed, 30 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> > index b05d9c85384b..356ac04093e8 100644
> > --- a/drivers/gpu/drm/i915/intel_display.c
> > +++ b/drivers/gpu/drm/i915/intel_display.c
> > @@ -13031,6 +13031,17 @@ static int intel_atomic_commit(struct drm_device *dev,
> >  	struct drm_i915_private *dev_priv = to_i915(dev);
> >  	int ret = 0;
> >  
> > +	/*
> > +	 * The intel_legacy_cursor_update() fast path takes care
> > +	 * of avoiding the vblank waits for simple cursor
> > +	 * movement and flips. For cursor on/off and size changes,
> > +	 * we want to perform the vblank waits so that watermark
> > +	 * updates happen during the correct frames. Gen9+ have
> > +	 * double buffered watermarks and so shouldn't need this.
> > +	 */
> > +	if (INTEL_GEN(dev_priv) < 9)
> > +		state->legacy_cursor_update = false;
> Could we perhaps add a check in ilk_compute_pipe_wm which unsets the legacy_cursor_update flag so we keep things unsynced as much as possible?

I'd have to sprinkle that stuff everywhere but the SKL code
eventually. Seems a little pointless when I can just plop it
there.

> >  	ret = drm_atomic_helper_setup_commit(state, nonblock);
> >  	if (ret)
> >  		return ret;
> > @@ -13455,8 +13466,7 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> >  	    old_plane_state->src_h != src_h ||
> >  	    old_plane_state->crtc_w != crtc_w ||
> >  	    old_plane_state->crtc_h != crtc_h ||
> > -	    !old_plane_state->visible ||
> > -	    old_plane_state->fb->modifier != fb->modifier)
> > +	    !old_plane_state->fb != !fb)
> >  		goto slow;
> >  
> >  	new_plane_state = intel_plane_duplicate_state(plane);
> > @@ -13479,10 +13489,6 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> >  	if (ret)
> >  		goto out_free;
> >  
> > -	/* Visibility changed, must take slowpath. */
> > -	if (!new_plane_state->visible)
> > -		goto slow_free;
> > -
> >  	ret = mutex_lock_interruptible(&dev_priv->drm.struct_mutex);
> >  	if (ret)
> >  		goto out_free;
> Those 2 hunks are needed. If you move the cursor out of the visible area or back you need to update.

No. I changed the wm code to consider a non-visible but logicall active
cursor as needing proper watermarks. That avoids needing this fallback
path here.

> Easiest way to trigger a bug is load a 256 width cursor out of the visible area, move it back in and you get
> a fifo underrun.
> 
> Why is switching fb's synced?

It is not.

> Identical sized fb should be unsynced if possible.
>
> > @@ -13522,9 +13528,12 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> >  	new_plane_state->fb = old_fb;
> >  	to_intel_plane_state(new_plane_state)->vma = old_vma;
> >  
> > -	intel_plane->update_plane(plane,
> > -				  to_intel_crtc_state(crtc->state),
> > -				  to_intel_plane_state(plane->state));
> > +	if (plane->state->visible)
> > +		intel_plane->update_plane(plane,
> > +					  to_intel_crtc_state(crtc->state),
> > +					  to_intel_plane_state(plane->state));
> > +	else
> > +		intel_plane->disable_plane(plane, crtc);
> >  
> >  	intel_cleanup_plane_fb(plane, new_plane_state);
> >  
> > @@ -13534,8 +13543,6 @@ intel_legacy_cursor_update(struct drm_plane *plane,
> >  	intel_plane_destroy_state(plane, new_plane_state);
> >  	return ret;
> >  
> > -slow_free:
> > -	intel_plane_destroy_state(plane, new_plane_state);
> >  slow:
> >  	return drm_atomic_helper_update_plane(plane, crtc, fb,
> >  					      crtc_x, crtc_y, crtc_w, crtc_h,
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> > index fe243c65de1a..4de8c40acc7e 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -1831,20 +1831,24 @@ static uint32_t ilk_compute_cur_wm(const struct intel_crtc_state *cstate,
> >  				   const struct intel_plane_state *pstate,
> >  				   uint32_t mem_value)
> >  {
> > +	int cpp;
> > +
> >  	/*
> > -	 * We treat the cursor plane as always-on for the purposes of watermark
> > -	 * calculation.  Until we have two-stage watermark programming merged,
> > -	 * this is necessary to avoid flickering.
> > +	 * Treat cursor with fb as always visible since cursor updates
> > +	 * can happen faster than the vrefresh rate, and the current
> > +	 * watermark code doesn't handle that correctly. Cursor updates
> > +	 * which set/clear the fb or change the cursor size are going
> > +	 * to get throttled by intel_legacy_cursor_update() to work
> > +	 * around this problem with the watermark code.
> >  	 */
> > -	int cpp = 4;
> > -	int width = pstate->base.visible ? pstate->base.crtc_w : 64;
> > -
> > -	if (!cstate->base.active)
> > +	if (!cstate->base.active || !pstate->base.fb)
> >  		return 0;
> >  
> > +	cpp = pstate->base.fb->format->cpp[0];
> > +
> >  	return ilk_wm_method2(cstate->pixel_rate,
> >  			      cstate->base.adjusted_mode.crtc_htotal,
> > -			      width, cpp, mem_value);
> > +			      pstate->base.crtc_w, cpp, mem_value);
> >  }
> >  
> >  /* Only for WM_LP. */
> 

-- 
Ville Syrjälä
Intel OTC
_______________________________________________
Intel-gfx mailing list
Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/intel-gfx




[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]
  Powered by Linux