[PATCH 9/9] drm/i915: Avoid sleeping inside per-engine reset

[Chris Wilson]

Only sleep and repeat when asked for a full device reset (ALL_ENGINES)
and avoid using sleeping waits when asked for a per-engine reset. The
goal is to be able to use a per-engine reset from hardirq/softirq/timer
context. A consequence is that our individual wait timeouts are a
thousand times shorter, on the order of a hundred microseconds rather
than hundreds of millisecond. This may make hitting the timeouts more
common, but hopefully the fallover to the full-device reset will be
sufficient to pick up the pieces.

Note, that the sleeps inside older gen (pre-gen8) have been left as they
are only used in full device reset mode.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Cc: Michał Winiarski <michal.winiarski at intel.com>
CC: Michel Thierry <michel.thierry at intel.com>
Cc: Jeff McGee <jeff.mcgee at intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 31 ++++++++++++++++---------------
 1 file changed, 16 insertions(+), 15 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 44c4654443ba..9fa60d8f897e 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1702,11 +1702,10 @@ static void gen3_stop_engine(struct intel_engine_cs *engine)
 	const i915_reg_t mode = RING_MI_MODE(base);
 
 	I915_WRITE_FW(mode, _MASKED_BIT_ENABLE(STOP_RING));
-	if (intel_wait_for_register_fw(dev_priv,
-				       mode,
-				       MODE_IDLE,
-				       MODE_IDLE,
-				       500))
+	if (__intel_wait_for_register_fw(dev_priv,
+					 mode, MODE_IDLE, MODE_IDLE,
+					 500, 0,
+					 NULL))
 		DRM_DEBUG_DRIVER("%s: timed out on STOP_RING\n",
 				 engine->name);
 
@@ -1860,9 +1859,10 @@ static int gen6_hw_domain_reset(struct drm_i915_private *dev_priv,
 	__raw_i915_write32(dev_priv, GEN6_GDRST, hw_domain_mask);
 
 	/* Wait for the device to ack the reset requests */
-	err = intel_wait_for_register_fw(dev_priv,
-					  GEN6_GDRST, hw_domain_mask, 0,
-					  500);
+	err = __intel_wait_for_register_fw(dev_priv,
+					   GEN6_GDRST, hw_domain_mask, 0,
+					   500, 0,
+					   NULL);
 	if (err)
 		DRM_DEBUG_DRIVER("Wait for 0x%08x engines reset failed\n",
 				 hw_domain_mask);
@@ -2027,11 +2027,12 @@ static int gen8_reset_engine_start(struct intel_engine_cs *engine)
 	I915_WRITE_FW(RING_RESET_CTL(engine->mmio_base),
 		      _MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));
 
-	ret = intel_wait_for_register_fw(dev_priv,
-					 RING_RESET_CTL(engine->mmio_base),
-					 RESET_CTL_READY_TO_RESET,
-					 RESET_CTL_READY_TO_RESET,
-					 700);
+	ret = __intel_wait_for_register_fw(dev_priv,
+					   RING_RESET_CTL(engine->mmio_base),
+					   RESET_CTL_READY_TO_RESET,
+					   RESET_CTL_READY_TO_RESET,
+					   700, 0,
+					   NULL);
 	if (ret)
 		DRM_ERROR("%s: reset request timeout\n", engine->name);
 
@@ -2094,7 +2095,7 @@ int intel_gpu_reset(struct drm_i915_private *dev_priv, unsigned engine_mask)
 	int retry;
 	int ret;
 
-	might_sleep();
+	might_sleep_if(engine_mask == ALL_ENGINES);
 
 	/* If the power well sleeps during the reset, the reset
 	 * request may be dropped and never completes (causing -EIO).
@@ -2120,7 +2121,7 @@ int intel_gpu_reset(struct drm_i915_private *dev_priv, unsigned engine_mask)
 			GEM_TRACE("engine_mask=%x\n", engine_mask);
 			ret = reset(dev_priv, engine_mask);
 		}
-		if (ret != -ETIMEDOUT)
+		if (ret != -ETIMEDOUT || engine_mask != ALL_ENGINES)
 			break;
 
 		cond_resched();
-- 
2.16.3