On 08/02/2018 16:04, Chris Wilson wrote:
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
Ping Ville - ack? Regards, Tvrtko _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
