[PATCH 5.5 220/257] drm/i915/gt: Treat idling as a RPS downclock event

From: Greg Kroah-Hartman
Date: Thu Apr 16 2020 - 11:35:11 EST


From: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>

commit 98479ada421a8fd2123b98efd398a6f1379307ab upstream.

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: 3e7abf814193 ("drm/i915: Extract GT render power state management")
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Andi Shyti <andi.shyti@xxxxxxxxx>
Cc: Lyude Paul <lyude@xxxxxxxxxx>
Reviewed-by: Andi Shyti <andi.shyti@xxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20200322163225.28791-1-chris@xxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v5.5+
(cherry picked from commit 21abf0bf168dffff1192e0f072af1dc74ae1ff0e)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
drivers/gpu/drm/i915/gt/intel_rps.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -763,6 +763,19 @@ void intel_rps_park(struct intel_rps *rp
intel_uncore_forcewake_get(rps_to_uncore(rps), FORCEWAKE_MEDIA);
rps_set(rps, rps->idle_freq);
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)