From b68763741aa29f2541c7ca58bcb0c2bb6cb5f449 Mon Sep 17 00:00:00 2001
From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Date: Tue, 5 Dec 2017 13:28:54 +0000
Subject: [PATCH] drm/i915: Restore GT performance in headless mode with DMC loaded
Git-commit: b68763741aa29f2541c7ca58bcb0c2bb6cb5f449
Patch-mainline: v4.16-rc1
References: FATE#322643 bsc#1055900
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.
CNL has the same problem which will be addressed as a follow-up. Doing
that requires a fix for a DC6 context corruption problem in the CNL DMC
firmware which is yet to be released.
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)
V6: * Drop the NEEDS_CSR_GT_PERF_WA macro since all firmwares have now been deployed. (Imre, Chris)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=100572
Testcase: igt/gem_exec_nop/headless
Cc: Imre Deak <imre.deak@intel.com>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk> (v2)
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Dmitry Rogozhkin <dmitry.v.rogozhkin@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> (v5)
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
[imre: Add note about applying the WA on CNL as a follow-up]
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171205132854.26380-1-tvrtko.ursulin@linux.intel.com
Acked-by: Takashi Iwai <tiwai@suse.de>
---
drivers/gpu/drm/i915/i915_drv.h | 1 +
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 | 5 +++++
4 files changed, 23 insertions(+)
--- 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,
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -3386,6 +3386,9 @@ i915_gem_idle_work_handler(struct work_s
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);
--- 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_pr
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);
--- 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 inte
return "INIT";
case POWER_DOMAIN_MODESET:
return "MODESET";
+ case POWER_DOMAIN_GT_IRQ:
+ return "GT_IRQ";
default:
MISSING_CASE(domain);
return "?";
@@ -1715,6 +1717,7 @@ void intel_display_power_put(struct drm_
BIT_ULL(POWER_DOMAIN_INIT))
#define SKL_DISPLAY_DC_OFF_POWER_DOMAINS ( \
SKL_DISPLAY_POWERWELL_2_POWER_DOMAINS | \
+ BIT_ULL(POWER_DOMAIN_GT_IRQ) | \
BIT_ULL(POWER_DOMAIN_MODESET) | \
BIT_ULL(POWER_DOMAIN_AUX_A) | \
BIT_ULL(POWER_DOMAIN_INIT))
@@ -1737,6 +1740,7 @@ void intel_display_power_put(struct drm_
BIT_ULL(POWER_DOMAIN_INIT))
#define BXT_DISPLAY_DC_OFF_POWER_DOMAINS ( \
BXT_DISPLAY_POWERWELL_2_POWER_DOMAINS | \
+ BIT_ULL(POWER_DOMAIN_GT_IRQ) | \
BIT_ULL(POWER_DOMAIN_MODESET) | \
BIT_ULL(POWER_DOMAIN_AUX_A) | \
BIT_ULL(POWER_DOMAIN_INIT))
@@ -1795,6 +1799,7 @@ void intel_display_power_put(struct drm_
BIT_ULL(POWER_DOMAIN_INIT))
#define GLK_DISPLAY_DC_OFF_POWER_DOMAINS ( \
GLK_DISPLAY_POWERWELL_2_POWER_DOMAINS | \
+ BIT_ULL(POWER_DOMAIN_GT_IRQ) | \
BIT_ULL(POWER_DOMAIN_MODESET) | \
BIT_ULL(POWER_DOMAIN_AUX_A) | \
BIT_ULL(POWER_DOMAIN_GMBUS) | \