From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
It seems that the DMC likes to transition between the DC states a lot when
there are no connected displays (no active power domains) during command
submission.
This activity on DC states has a negative impact on the performance of the
chip with huge latencies observed in the interrupt handlers and elsewhere.
Simple tests like igt/gem_latency -n 0 are slowed down by a factor of
eight.
Work around it by introducing a new power domain named,
POWER_DOMAIN_GT_IRQ, associtated with the "DC off" power well, which is
held for the duration of command submission activity.
v2:
* Add commit text as comment in i915_gem_mark_busy. (Chris Wilson)
* Protect macro body with braces. (Jani Nikula)
v3:
* Add dedicated power domain for clarity. (Chris, Imre)
* Commit message and comment text updates.
* Apply to all big-core GEN9 parts apart for Skylake which is pending DMC
firmware release.
v4:
* Power domain should be inner to device runtime pm. (Chris)
* Simplify NEEDS_CSR_GT_PERF_WA macro. (Chris)
* Handle async DMC loading by moving the GT_IRQ power domain logic into
intel_runtime_pm. (Daniel, Chris)
* Include small core GEN9 as well. (Imre)
v5
* Special handling for async DMC load is not needed since on failure the
power domain reference is kept permanently taken. (Imre)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100572
Testcase: igt/gem_exec_nop/headless
Cc: Imre Deak <imre.deak@xxxxxxxxx>
Acked-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> (v2)
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_drv.h | 4 ++++
drivers/gpu/drm/i915/i915_gem.c | 3 +++
drivers/gpu/drm/i915/i915_gem_request.c | 14 ++++++++++++++
drivers/gpu/drm/i915/intel_runtime_pm.c | 14 ++++++++++++++
4 files changed, 35 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index bddd65839f60..59cf11dd5d3b 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -398,6 +398,7 @@ enum intel_display_power_domain {
POWER_DOMAIN_AUX_D,
POWER_DOMAIN_GMBUS,
POWER_DOMAIN_MODESET,
+ POWER_DOMAIN_GT_IRQ,
POWER_DOMAIN_INIT,
POWER_DOMAIN_NUM,
@@ -3285,6 +3286,9 @@ intel_info(const struct drm_i915_private *dev_priv)
#define GT_FREQUENCY_MULTIPLIER 50
#define GEN9_FREQ_SCALER 3
+#define NEEDS_CSR_GT_PERF_WA(dev_priv) \
+ (HAS_CSR(dev_priv) && IS_GEN9(dev_priv) && !IS_SKYLAKE(dev_priv))
+
#include "i915_trace.h"
static inline bool intel_vtd_active(void)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 354b0546a191..c6067cba1dca 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3381,6 +3381,9 @@ i915_gem_idle_work_handler(struct work_struct *work)
if (INTEL_GEN(dev_priv) >= 6)
gen6_rps_idle(dev_priv);
+
+ intel_display_power_put(dev_priv, POWER_DOMAIN_GT_IRQ);
+
intel_runtime_pm_put(dev_priv);
out_unlock:
mutex_unlock(&dev_priv->drm.struct_mutex);
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index a90bdd26571f..c28a4ceb016d 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -252,6 +252,20 @@ static void mark_busy(struct drm_i915_private *i915)
GEM_BUG_ON(!i915->gt.active_requests);
intel_runtime_pm_get_noresume(i915);
+
+ /*
+ * It seems that the DMC likes to transition between the DC states a lot
+ * when there are no connected displays (no active power domains) during
+ * command submission.
+ *
+ * This activity has negative impact on the performance of the chip with
+ * huge latencies observed in the interrupt handler and elsewhere.
+ *
+ * Work around it by grabbing a GT IRQ power domain whilst there is any
+ * GT activity, preventing any DC state transitions.
+ */
+ intel_display_power_get(i915, POWER_DOMAIN_GT_IRQ);
+
i915->gt.awake = true;
intel_enable_gt_powersave(i915);
diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
index 8315499452dc..48ad0828ace7 100644
--- a/drivers/gpu/drm/i915/intel_runtime_pm.c
+++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
@@ -130,6 +130,8 @@ intel_display_power_domain_str(enum intel_display_power_domain domain)
return "INIT";
case POWER_DOMAIN_MODESET:
return "MODESET";
+ case POWER_DOMAIN_GT_IRQ:
+ return "GT_IRQ";
default:
MISSING_CASE(domain);
return "?";
@@ -1471,6 +1473,9 @@ void intel_display_power_get(struct drm_i915_private *dev_priv,
{
struct i915_power_domains *power_domains = &dev_priv->power_domains;
+ if (domain == POWER_DOMAIN_GT_IRQ && !NEEDS_CSR_GT_PERF_WA(dev_priv))
+ return;
