From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Somehow my SNB GT1 (Dell XPS 8300) gets very unhappy around
GPU hangs if the RPS EI/thresholds aren't suitably aligned.
It seems like scheduling/timer interupts stop working somehow
and things get stuck eg. in usleep_range().
I bisected the problem down to
commit 8a5864377b12 ("drm/i915/skl: Restructured the gen6_set_rps_thresholds function")
I observed that before all the values were at least multiples of 25,
but afterwards they are not. And rounding things up to the next multiple
of 25 does seem to help, so lets' do that. I also tried roundup(..., 5)
but that wasn't sufficient. Also I have no idea if we might need this sort of
thing on gen9+ as well.
These are the original EI/thresholds:
LOW_POWER
GEN6_RP_UP_EI 12500
GEN6_RP_UP_THRESHOLD 11800
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 21250
BETWEEN
GEN6_RP_UP_EI 10250
GEN6_RP_UP_THRESHOLD 9225
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 18750
HIGH_POWER
GEN6_RP_UP_EI 8000
GEN6_RP_UP_THRESHOLD 6800
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 15000
These are after 8a5864377b12:
LOW_POWER
GEN6_RP_UP_EI 12500
GEN6_RP_UP_THRESHOLD 11875
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 21250
BETWEEN
GEN6_RP_UP_EI 10156
GEN6_RP_UP_THRESHOLD 9140
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 18750
HIGH_POWER
GEN6_RP_UP_EI 7812
GEN6_RP_UP_THRESHOLD 6640
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 15000
And these are what we have after this patch:
LOW_POWER
GEN6_RP_UP_EI 12500
GEN6_RP_UP_THRESHOLD 11875
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 21250
BETWEEN
GEN6_RP_UP_EI 10175
GEN6_RP_UP_THRESHOLD 9150
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 18750
HIGH_POWER
GEN6_RP_UP_EI 7825
GEN6_RP_UP_THRESHOLD 6650
GEN6_RP_DOWN_EI 25000
GEN6_RP_DOWN_THRESHOLD 15000
Cc: stable@xxxxxxxxxxxxxxx
Cc: Akash Goel <akash.goel@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Testcase: igt/kms_pipe_crc_basic/hang-read-crc-pipe-B
Fixes: 8a5864377b12 ("drm/i915/skl: Restructured the gen6_set_rps_thresholds function")
Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_reg.h | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index c21b71c86a6b..08f01f4470cd 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -2948,7 +2948,14 @@ enum skl_disp_power_wells {
#define GEN6_RP_STATE_CAP _MMIO(MCHBAR_MIRROR_BASE_SNB + 0x5998)
#define BXT_RP_STATE_CAP _MMIO(0x138170)
-#define INTERVAL_1_28_US(us) (((us) * 100) >> 7)
+/*
+ * Make these a multiple of magic 25 to avoid SNB (eg. Dell XPS
+ * 8300) freezing up around GPU hangs. Looks as if even
+ * scheduling/timer interrupts start misbehaving if the RPS
+ * EI/thresholds are "bad", leading to a very sluggish or even
+ * frozen machine.
+ */
+#define INTERVAL_1_28_US(us) roundup(((us) * 100) >> 7, 25)
#define INTERVAL_1_33_US(us) (((us) * 3) >> 2)
#define INTERVAL_0_833_US(us) (((us) * 6) / 5)
#define GT_INTERVAL_FROM_US(dev_priv, us) (IS_GEN9(dev_priv) ? \
--
2.7.4
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