FBC is currently disabled upstream due a few conflicting requirements and questionable benefit. It is also buggy...
https://bugs.freedesktop.org/show_bug.cgi?id=33487 is the current open SNB bug where FBC prevents the screen from being redrawn under a compositing WM. At last it appears that we have found the cause and a solution, so please do give these patches some testing - you will need to pass i915.i915_enable_fbc=1 to override the forced disabling of FBC. 1-2: tidy up some spurious code in the fbc routines. 1 is very confused indeed. 3: Enables persistent-mode for ILK/SNB which the documentation and discussion suggests is necessary for correct front-buffer rendering, such as X. I wonder if this then relates to https://bugs.freedesktop.org/show_bug.cgi?id=3174 4: Demonstrates the problem encountered with mixed-mode compositors (i.e. they combine page-flipping with copy-sub-buffer blits). The simple solution here comes at a cost though - it will halve the vsync'ed update rate. Note that this problem is universal to our implementation of FBC. 5: Prepares the way for the solution to the performance regression, this could be done in conjunction with 1/2, and unexports the chipset specific routines and forces the couple of external callers of disable FBC through the generic interface which is about to gain some extra complications... 6: Defers intel_enable_fbc() by 50ms to ensure that page-flipping has completed before incurring a slow and synchronous restart of FBC. -Chris _______________________________________________ Intel-gfx mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/intel-gfx
