[Intel-gfx] [PATCH] drm/i915/gt: Prefer soft-rc6 over RPS DOWN_TIMEOUT

[Chris Wilson]

The RPS DOWN_TIMEOUT interrupt is signaled after a period of rc6, and
upon receipt of that interrupt we reprogram the GPU clocks down to the
next idle notch [to help convserve power during rc6]. However, on
execlists, we benefit from soft-rc6 immediately parking the GPU and
setting idle frequencies upon idling [within a jiffie], and here the
interrupt prevents us from restarting from our last frequency.

In the process, we can simply opt for a static pm_events mask and rely
on the enable/disable interrupts to flush the worker on parking.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/gt/intel_rps.c | 38 ++++++++++++++---------------
 1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/intel_rps.c b/drivers/gpu/drm/i915/gt/intel_rps.c
index 4dcfae16a7ce..1c5488f3a8d7 100644
--- a/drivers/gpu/drm/i915/gt/intel_rps.c
+++ b/drivers/gpu/drm/i915/gt/intel_rps.c
@@ -57,7 +57,7 @@ static u32 rps_pm_mask(struct intel_rps *rps, u8 val)
 	if (val < rps->max_freq_softlimit)
 		mask |= GEN6_PM_RP_UP_EI_EXPIRED | GEN6_PM_RP_UP_THRESHOLD;
 
-	mask &= READ_ONCE(rps->pm_events);
+	mask &= rps->pm_events;
 
 	return rps_pm_sanitize_mask(rps, ~mask);
 }
@@ -74,15 +74,6 @@ static void rps_enable_interrupts(struct intel_rps *rps)
 
 	rps_reset_ei(rps);
 
-	if (IS_VALLEYVIEW(gt->i915))
-		/* WaGsvRC0ResidencyMethod:vlv */
-		events = GEN6_PM_RP_UP_EI_EXPIRED;
-	else
-		events = (GEN6_PM_RP_UP_THRESHOLD |
-			  GEN6_PM_RP_DOWN_THRESHOLD |
-			  GEN6_PM_RP_DOWN_TIMEOUT);
-	WRITE_ONCE(rps->pm_events, events);
-
 	spin_lock_irq(&gt->irq_lock);
 	gen6_gt_pm_enable_irq(gt, rps->pm_events);
 	spin_unlock_irq(&gt->irq_lock);
@@ -919,12 +910,10 @@ static bool gen9_rps_enable(struct intel_rps *rps)
 		intel_uncore_write_fw(uncore, GEN6_RC_VIDEO_FREQ,
 				      GEN9_FREQUENCY(rps->rp1_freq));
 
-	/* 1 second timeout */
-	intel_uncore_write_fw(uncore, GEN6_RP_DOWN_TIMEOUT,
-			      GT_INTERVAL_FROM_US(i915, 1000000));
-
 	intel_uncore_write_fw(uncore, GEN6_RP_IDLE_HYSTERSIS, 0xa);
 
+	rps->pm_events = GEN6_PM_RP_UP_THRESHOLD | GEN6_PM_RP_DOWN_THRESHOLD;
+
 	return rps_reset(rps);
 }
 
@@ -935,12 +924,10 @@ static bool gen8_rps_enable(struct intel_rps *rps)
 	intel_uncore_write_fw(uncore, GEN6_RC_VIDEO_FREQ,
 			      HSW_FREQUENCY(rps->rp1_freq));
 
-	/* NB: Docs say 1s, and 1000000 - which aren't equivalent */
-	intel_uncore_write_fw(uncore, GEN6_RP_DOWN_TIMEOUT,
-			      100000000 / 128); /* 1 second timeout */
-
 	intel_uncore_write_fw(uncore, GEN6_RP_IDLE_HYSTERSIS, 10);
 
+	rps->pm_events = GEN6_PM_RP_UP_THRESHOLD | GEN6_PM_RP_DOWN_THRESHOLD;
+
 	return rps_reset(rps);
 }
 
@@ -952,6 +939,10 @@ static bool gen6_rps_enable(struct intel_rps *rps)
 	intel_uncore_write_fw(uncore, GEN6_RP_DOWN_TIMEOUT, 50000);
 	intel_uncore_write_fw(uncore, GEN6_RP_IDLE_HYSTERSIS, 10);
 
+	rps->pm_events = (GEN6_PM_RP_UP_THRESHOLD |
+			  GEN6_PM_RP_DOWN_THRESHOLD |
+			  GEN6_PM_RP_DOWN_TIMEOUT);
+
 	return rps_reset(rps);
 }
 
@@ -1037,6 +1028,10 @@ static bool chv_rps_enable(struct intel_rps *rps)
 			      GEN6_RP_UP_BUSY_AVG |
 			      GEN6_RP_DOWN_IDLE_AVG);
 
+	rps->pm_events = (GEN6_PM_RP_UP_THRESHOLD |
+			  GEN6_PM_RP_DOWN_THRESHOLD |
+			  GEN6_PM_RP_DOWN_TIMEOUT);
+
 	/* Setting Fixed Bias */
 	vlv_punit_get(i915);
 
@@ -1135,6 +1130,9 @@ static bool vlv_rps_enable(struct intel_rps *rps)
 			      GEN6_RP_UP_BUSY_AVG |
 			      GEN6_RP_DOWN_IDLE_CONT);
 
+	/* WaGsvRC0ResidencyMethod:vlv */
+	rps->pm_events = GEN6_PM_RP_UP_EI_EXPIRED;
+
 	vlv_punit_get(i915);
 
 	/* Setting Fixed Bias */
@@ -1469,7 +1467,7 @@ static void rps_work(struct work_struct *work)
 	u32 pm_iir = 0;
 
 	spin_lock_irq(&gt->irq_lock);
-	pm_iir = fetch_and_zero(&rps->pm_iir) & READ_ONCE(rps->pm_events);
+	pm_iir = fetch_and_zero(&rps->pm_iir) & rps->pm_events;
 	client_boost = atomic_read(&rps->num_waiters);
 	spin_unlock_irq(&gt->irq_lock);
 
@@ -1572,7 +1570,7 @@ void gen6_rps_irq_handler(struct intel_rps *rps, u32 pm_iir)
 	struct intel_gt *gt = rps_to_gt(rps);
 	u32 events;
 
-	events = pm_iir & READ_ONCE(rps->pm_events);
+	events = pm_iir & rps->pm_events;
 	if (events) {
 		spin_lock(&gt->irq_lock);
 
-- 
2.20.1