On Thu, Jul 03, 2025 at 03:12:39PM +0300, Jani Nikula wrote: > On Thu, 03 Jul 2025, Ville Syrjala <[email protected]> wrote: > > From: Ville Syrjälä <[email protected]> > > > > Make sure poll_timeout_us() works by using it in i915 > > instead of the custom __wait_for(). > > > > Remaining difference between two: > > | poll_timeout_us() | __wait_for() > > --------------------------------------------------- > > backoff | fixed interval | exponential > > usleep_range() | N/4+1 to N | N to N*2 > > clock | MONOTONIC | MONOTONIC_RAW > > > > Just a test hack for now, proper conversion probably > > needs actual thought. > > Agreed. > > I feel pretty strongly about converting everything to use > poll_timeout_us() and poll_timeout_us_atomic() directly. I think the > plethora of wait_for variants in i915_utils.h is more confusing than > helpful (even if some of them are supposed to be "simpler" > alternatives). I also think the separate atomic variant is better than > magically deciding that based on delay length. > > I'm also not all that convinced about the exponential wait. Not all of > the wait_for versions use it, and then it needs to have a max wait > anyway (we have an issue with xe not having that [1]). I believe callers > can decide on a sleep length that is appropriate for the timeout, case > by case, and gut feeling says it's probably fine. ;)
Yeah, we've not really done any work to justify the polling interval/backoff strategy. At some point it would be nice to collect some statistics to see what the typical wait durations are, and then perhaps tune the polling interval on a case by case basis to be at least somewhat optimal (short enough to not cause significant delays, but long enough to avoid excessive polling). -- Ville Syrjälä Intel
