drm/i915/gt: Treat idling as a RPS downclock event

If we park/unpark faster than we can respond to RPS events, we never
will process a downclock event after expiring a waitboost, and thus we
will forever restart the GPU at max clocks even if the workload switches
and doesn't justify full power.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/1500
Fixes: 60057c8cc5ff ("drm/i915: Extract GT render power state management")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Andi Shyti <andi.shyti@intel.com>
Cc: Lyude Paul <lyude@redhat.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200322163225.28791-1-chris@chris-wilson.co.uk
Cc: <stable@vger.kernel.org> # v5.5+

diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index 7bf631ca560b77af54c547c766605ae580f198e0..2d906db2da577f72eba5361423f5bef32dd3ab40 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -771,6 +771,19 @@ void intel_rps_park(struct intel_rps *rps)
        intel_uncore_forcewake_get(rps_to_uncore(rps), FORCEWAKE_MEDIA);
        rps_set(rps, rps->idle_freq, false);
        intel_uncore_forcewake_put(rps_to_uncore(rps), FORCEWAKE_MEDIA);
+
+       /*
+        * Since we will try and restart from the previously requested
+        * frequency on unparking, treat this idle point as a downclock
+        * interrupt and reduce the frequency for resume. If we park/unpark
+        * more frequently than the rps worker can run, we will not respond
+        * to any EI and never see a change in frequency.
+        *
+        * (Note we accommodate Cherryview's limitation of only using an
+        * even bin by applying it to all.)
+        */
+       rps->cur_freq =
+               max_t(int, round_down(rps->cur_freq - 1, 2), rps->min_freq);
 }
 
 void intel_rps_boost(struct i915_request *rq)