Re: [Intel-gfx] [PATCH v2 14/14] drm/i915/fbc: Reallocate cfb if we need more of it

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

On Tue, Dec 03, 2019 at 09:45:19AM +0100, Maarten Lankhorst wrote:
> Op 29-11-2019 om 12:37 schreef Ville Syrjälä:
> > On Fri, Nov 29, 2019 at 09:48:45AM +0100, Maarten Lankhorst wrote:
> >> Op 28-11-2019 om 16:59 schreef Ville Syrjälä:
> >>> On Thu, Nov 28, 2019 at 04:48:04PM +0100, Maarten Lankhorst wrote:
> >>>> Op 27-11-2019 om 21:12 schreef Ville Syrjala:
> >>>>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>>>>
> >>>>> The code assumes we can omit the cfb allocation once fbc
> >>>>> has been enabled once. That's nonsense. Let's try to
> >>>>> reallocate it if we need to.
> >>>>>
> >>>>> The code is still a mess, but maybe this is enough to get
> >>>>> fbc going in some cases where it initially underallocates
> >>>>> the cfb and there's no full modeset to fix it up.
> >>>>>
> >>>>> Cc: Daniel Drake <drake@endlessm.com>
> >>>>> Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
> >>>>> Cc: Jian-Hong Pan <jian-hong@endlessm.com>
> >>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> >>>>> ---
> >>>>>  drivers/gpu/drm/i915/display/intel_fbc.c | 22 +++++++++++++++-------
> >>>>>  1 file changed, 15 insertions(+), 7 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
> >>>>> index c976698b0729..928059a5da80 100644
> >>>>> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> >>>>> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> >>>>> @@ -672,6 +672,14 @@ static void intel_fbc_update_state_cache(struct intel_crtc *crtc,
> >>>>>  		cache->fence_id = -1;
> >>>>>  }
> >>>>>  
> >>>>> +static bool intel_fbc_cfb_size_changed(struct drm_i915_private *dev_priv)
> >>>>> +{
> >>>>> +	struct intel_fbc *fbc = &dev_priv->fbc;
> >>>>> +
> >>>>> +	return intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache) >
> >>>>> +		fbc->compressed_fb.size * fbc->threshold;
> >>>>> +}
> >>>>> +
> >>>>>  static bool intel_fbc_can_activate(struct intel_crtc *crtc)
> >>>>>  {
> >>>>>  	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
> >>>>> @@ -757,8 +765,7 @@ static bool intel_fbc_can_activate(struct intel_crtc *crtc)
> >>>>>  	 * we didn't get any invalidate/deactivate calls, but this would require
> >>>>>  	 * a lot of tracking just for a specific case. If we conclude it's an
> >>>>>  	 * important case, we can implement it later. */
> >>>>> -	if (intel_fbc_calculate_cfb_size(dev_priv, &fbc->state_cache) >
> >>>>> -	    fbc->compressed_fb.size * fbc->threshold) {
> >>>>> +	if (intel_fbc_cfb_size_changed(dev_priv)) {
> >>>>>  		fbc->no_fbc_reason = "CFB requirements changed";
> >>>>>  		return false;
> >>>>>  	}
> >>>>> @@ -1112,12 +1119,12 @@ void intel_fbc_enable(struct intel_crtc *crtc,
> >>>>>  	mutex_lock(&fbc->lock);
> >>>>>  
> >>>>>  	if (fbc->crtc) {
> >>>>> -		WARN_ON(fbc->crtc == crtc && !crtc_state->enable_fbc);
> >>>>> -		goto out;
> >>>>> -	}
> >>>>> +		if (fbc->crtc != crtc ||
> >>>>> +		    !intel_fbc_cfb_size_changed(dev_priv))
> >>>>> +			goto out;
> >>>>>  
> >>>>> -	if (!crtc_state->enable_fbc)
> >>>>> -		goto out;
> >>>>> +		__intel_fbc_disable(dev_priv);
> >>>>> +	}
> >>>>>  
> >>>>>  	WARN_ON(fbc->active);
> >>>>>  
> >>>>> @@ -1130,6 +1137,7 @@ void intel_fbc_enable(struct intel_crtc *crtc,
> >>>>>  	if (intel_fbc_alloc_cfb(dev_priv,
> >>>>>  				intel_fbc_calculate_cfb_size(dev_priv, cache),
> >>>>>  				fb->format->cpp[0])) {
> >>>>> +		cache->plane.visible = false;
> >>>>>  		fbc->no_fbc_reason = "not enough stolen memory";
> >>>>>  		goto out;
> >>>>>  	}
> >>>> Makes sense, unfortunately kms_cursor_legacy starts failing on this series. :(
> >>>>
> >>>> For 1-11, 14
> >>>>
> >>>> Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>>
> >>>> We should probably get rid of the FBC disable on frontbuffer disable as well. I had some patches but nothing upstream-worthy yet. :(
> >>> How would we get rid of the disable there? By triggering nukes at some
> >>> predefined interval? Doesn't sound all that great.
> >> Not touching FBC on frontbuffer write at all, and forcing userspace to use the dirtyfb api. I think the whole implicit tracking should be removed.
> > Perhaps. Not sure userspace is ready for that though.
> 
> We have to audit that DirtyFB is called on all gen9+ userspace, because FBC is only enabled by default on those platforms.

I'll probably enable it across the board once I get it fixed.

> 
> I know the modesetting ddx does, I believe xf86-video-intel as well. So it should be safe to do. We could hide the old behavior behind a kernel parameter for now for 1 or 2 releases,
> 
> so we can chicken out if needed.
> 
> > I guess the only long lasting frontbuffer invalidate is the
> > one from set_domain. Everything else is bounded and so we
> > know the flush is going to come in a somewhat timely manner.
> > So for those cases I guess we could perhaps skip the invalidate.
> >
> > Hmm. Also looks like ORIGIN_GTT has been neutered and now
> > we treat everyting as ORIGIN_CPU. That's maybe not so great.
> > Should probably reinstate ORIGIN_GTT so we can actually benefit
> > from the hw gtt tracking. Or we just try to kill that off as well.
> HW tracking has been buggy for a long time, and is no longer available on current hw because of those bugs.

Which bugs? We still enable it on all platforms so I don't know what
you mean by it not being available.

> > Also I wonder where is the flush counterpart to the invalidate
> > in i915_gem_object_prepare_write()?
> >
> Not sure.

-- 
Ville Syrjälä
Intel
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