On Tue, Nov 18, 2014 at 9:02 AM, Daniel Vetter <daniel@xxxxxxxx> wrote: > On Mon, Nov 03, 2014 at 01:29:04PM +0000, Dave Gordon wrote: >> Fixes to both the LRC and the legacy ringbuffer code to correctly >> calculate and update the available space in a ring. >> >> The logical ring code was updating the software ring 'head' value >> by reading the hardware 'HEAD' register. In LRC mode, this is not >> valid as the hardware is not necessarily executing the same context >> that is being processed by the software. Thus reading the h/w HEAD >> could put an unrelated (undefined, effectively random) value into >> the s/w 'head' -- A Bad Thing for the free space calculations. >> >> In addition, the old code could update a ringbuffer's 'head' value >> from the 'last_retired_head' even when the latter hadn't been recently >> updated and therefore had a value of -1; this would also confuse the >> freespace calculations. Now, we consume 'last_retired_head' in just >> one place, ensuring that this confusion does not arise. >> >> Change-Id: Id7ce9096ed100a2882c68a54206f30b6c87e92fa >> Signed-off-by: Dave Gordon <david.s.gordon@xxxxxxxxx> > > Is there an igt testcase which readily reproduces this? Or can we have > one? Ping. Bugfixes really should have either a Testcase: line in the commit message indicating the igt used to reproduce/validate the fix or an explanation why testing with an igt case is not possible. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
