Quoting Tvrtko Ursulin (2018-02-08 16:00:36) > From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > > We can implement limited RC6 counter wrap-around protection under the > assumption that clients will be reading this value more frequently than > the wrap period on a given platform. > > With the typical wrap-around period being ~90 minutes, even with the > exception of Baytrail which wraps every 13 seconds, this sounds like a > reasonable assumption. > > Implementation works by storing a 64-bit software copy of a hardware RC6 > counter, along with the previous HW counter snapshot. This enables it to > detect wrap is polled frequently enough and keep the software copy > monotonically incrementing. > > v2: > * Missed GEN6_GT_GFX_RC6_LOCKED when considering slot sizing and > indexing. > * Fixed off-by-one in wrap-around handling. (Chris Wilson) > > v3: > * Simplify index checking by using unsigned int. (Chris Wilson) > * Expand the comment to explain why indexing works. > > v4: > * Use __int128 if supported. > > v5: > * Use mul_u64_u32_div. (Chris Wilson) > > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94852 > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> > Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> # v3 > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Ville better not complain he liked the round up behaviour :-p -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
