[PATCH 09/14] drm/i915: Skip reset request if there is one already

[Arun Siluvery]

From: Mika Kuoppala <mika.kuoppala at linux.intel.com>

To perform engine reset we first disable engine to capture its state. This
is done by issuing a reset request. Because we are reusing existing
infrastructure, again when we actually reset an engine, reset function
checks engine mask and issues reset request again which is unnecessary. To
avoid this we check if the engine is already prepared, if so we just exit
from that point.

Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 2017091..bafba2f 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1621,13 +1621,18 @@ static int wait_for_register_fw(struct drm_i915_private *dev_priv,
 static int gen8_request_engine_reset(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
+	const i915_reg_t reset_ctrl = RING_RESET_CTL(engine->mmio_base);
+	const u32 ready = RESET_CTL_REQUEST_RESET | RESET_CTL_READY_TO_RESET;
 	int ret;
 
-	I915_WRITE_FW(RING_RESET_CTL(engine->mmio_base),
-		      _MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));
+	/* If engine has been already prepared, we can shortcut here */
+	if ((I915_READ_FW(reset_ctrl) & ready) == ready)
+		return 0;
+
+	I915_WRITE_FW(reset_ctrl, _MASKED_BIT_ENABLE(RESET_CTL_REQUEST_RESET));
 
 	ret = wait_for_register_fw(dev_priv,
-				   RING_RESET_CTL(engine->mmio_base),
+				   reset_ctrl,
 				   RESET_CTL_READY_TO_RESET,
 				   RESET_CTL_READY_TO_RESET,
 				   700);
-- 
1.9.1