| Message ID | 1477065346-13736-1-git-send-email-paulo.r.zanoni@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Oct 21, 2016 at 01:55:45PM -0200, Paulo Zanoni wrote: > Broadwell and newer actually compress up to 2560 lines instead of 2048 > (as documented in the FBC_CTL page). If we don't take this into > consideration we end up reserving too little stolen memory for the > CFB, so we may allocate something else (such as a ring) right after > what we reserved, and the hardware will overwrite it with the contents > of the CFB when FBC is active, causing GPU hangs. Another possibility > is that the CFB may be allocated at the very end of the available > space, so the CFB will overlap the reserved stolen area, leading to > FIFO underruns. > > This bug has always been a problem on BDW (the only affected platform > where FBC is enabled by default), but it's much easier to reproduce > since the following commit: > commit c58b735fc762e891481e92af7124b85cb0a51fce > Author: Chris Wilson <chris@chris-wilson.co.uk> > Date: Thu Aug 18 17:16:57 2016 +0100 > drm/i915: Allocate rings from stolen > > Of course, you can only reproduce the bug if your screen is taller > than 2048 lines. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98213 > Fixes: a98ee79317b4 ("drm/i915/fbc: enable FBC by default on HSW and BDW") > Cc: <stable@vger.kernel.org> # v4.6+ > Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> > --- > drivers/gpu/drm/i915/intel_fbc.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c > index 617189a..6345cb8 100644 > --- a/drivers/gpu/drm/i915/intel_fbc.c > +++ b/drivers/gpu/drm/i915/intel_fbc.c > @@ -104,8 +104,10 @@ static int intel_fbc_calculate_cfb_size(struct drm_i915_private *dev_priv, > int lines; > > intel_fbc_get_plane_source_size(cache, NULL, &lines); > - if (INTEL_INFO(dev_priv)->gen >= 7) > + if (INTEL_GEN(dev_priv) == 7) > lines = min(lines, 2048); > + else if (INTEL_GEN(dev_priv) >= 8) > + lines = min(lines, 2560); > > /* Hardware needs the full buffer stride, not just the active area. */ > return lines * cache->fb.stride; > -- > 2.7.4 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c index 617189a..6345cb8 100644 --- a/drivers/gpu/drm/i915/intel_fbc.c +++ b/drivers/gpu/drm/i915/intel_fbc.c @@ -104,8 +104,10 @@ static int intel_fbc_calculate_cfb_size(struct drm_i915_private *dev_priv, int lines; intel_fbc_get_plane_source_size(cache, NULL, &lines); - if (INTEL_INFO(dev_priv)->gen >= 7) + if (INTEL_GEN(dev_priv) == 7) lines = min(lines, 2048); + else if (INTEL_GEN(dev_priv) >= 8) + lines = min(lines, 2560); /* Hardware needs the full buffer stride, not just the active area. */ return lines * cache->fb.stride;
Broadwell and newer actually compress up to 2560 lines instead of 2048 (as documented in the FBC_CTL page). If we don't take this into consideration we end up reserving too little stolen memory for the CFB, so we may allocate something else (such as a ring) right after what we reserved, and the hardware will overwrite it with the contents of the CFB when FBC is active, causing GPU hangs. Another possibility is that the CFB may be allocated at the very end of the available space, so the CFB will overlap the reserved stolen area, leading to FIFO underruns. This bug has always been a problem on BDW (the only affected platform where FBC is enabled by default), but it's much easier to reproduce since the following commit: commit c58b735fc762e891481e92af7124b85cb0a51fce Author: Chris Wilson <chris@chris-wilson.co.uk> Date: Thu Aug 18 17:16:57 2016 +0100 drm/i915: Allocate rings from stolen Of course, you can only reproduce the bug if your screen is taller than 2048 lines. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=98213 Fixes: a98ee79317b4 ("drm/i915/fbc: enable FBC by default on HSW and BDW") Cc: <stable@vger.kernel.org> # v4.6+ Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com> --- drivers/gpu/drm/i915/intel_fbc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)