From e396d2c10e352c28e812be90f515e8771021f16f Mon Sep 17 00:00:00 2001
From: Matthew Brost <matthew.brost@intel.com>
Date: Thu, 14 Oct 2021 10:19:44 -0700
Subject: drm/i915/guc: Don't call switch_to_kernel_context with GuC submission
Git-commit: 3633242927101b4bcff14cb0f718ecd4d346c5b1
Patch-mainline: v5.16-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225
Calling switch_to_kernel_context isn't needed if the engine PM reference
is taken while all user contexts are pinned as if don't have PM ref that
guarantees that all user contexts scheduling is disabled. By not calling
switch_to_kernel_context we save on issuing a request to the engine.
v2:
(Daniel Vetter)
- Add FIXME comment about pushing switch_to_kernel_context to backend
v3:
(John Harrison)
- Update commit message
- Fix workding comment
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211014172005.27155-5-matthew.brost@intel.com
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
drivers/gpu/drm/i915/gt/intel_engine_pm.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/drivers/gpu/drm/i915/gt/intel_engine_pm.c b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
index dacd62773735..a1334b48dde7 100644
--- a/drivers/gpu/drm/i915/gt/intel_engine_pm.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_pm.c
@@ -162,6 +162,19 @@ static bool switch_to_kernel_context(struct intel_engine_cs *engine)
unsigned long flags;
bool result = true;
+ /*
+ * This is execlist specific behaviour intended to ensure the GPU is
+ * idle by switching to a known 'safe' context. With GuC submission, the
+ * same idle guarantee is achieved by other means (disabling
+ * scheduling). Further, switching to a 'safe' context has no effect
+ * with GuC submission as the scheduler can just switch back again.
+ *
+ * FIXME: Move this backend scheduler specific behaviour into the
+ * scheduler backend.
+ */
+ if (intel_engine_uses_guc(engine))
+ return true;
+
/* GPU is pointing to the void, as good as in the kernel context. */
if (intel_gt_is_wedged(engine->gt))
return true;
--
2.38.1