[PATCH 06/20] drm/i915: Skip reset request if there is one already

[Michel Thierry]

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.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
Signed-off-by: Arun Siluvery <arun.siluvery at linux.intel.com>
Signed-off-by: Michel Thierry <michel.thierry at intel.com>
---
 drivers/gpu/drm/i915/intel_uncore.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 09f8ba4c79ee..d1a68775d04e 100644
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -1661,10 +1661,15 @@ int intel_wait_for_register(struct drm_i915_private *dev_priv,
 static int gen8_reset_engine_start(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 = intel_wait_for_register_fw(dev_priv,
 					 RING_RESET_CTL(engine->mmio_base),
-- 
2.11.0