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

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

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.

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.

Also I wonder where is the flush counterpart to the invalidate
in i915_gem_object_prepare_write()?

-- 
Ville Syrjälä
Intel
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