[Intel-gfx] [PATCH 3/3] drm/i915: Disable PSMI idle messaging when stopping ring

[Mika Kuoppala]

Hardware cannot be in a middle of idle flow messaging
when we pull the plug from ringbuffer. Disable idle
messaging before we do so to avoid potential deadlock
on engine initialization and reset.

v2: INVALID_MMIO_REG, unconditional enable (Chris)
v3: comment (Chris), bspec reference

References: bspec/11751
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/intel_engine_cs.c | 64 +++++++++++++++++++++++++-
 1 file changed, 63 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 2a94b92cfcd3..10cb6b22fe92 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -764,7 +764,7 @@ int intel_engine_init_common(struct intel_engine_cs *engine)
 
 /**
  * intel_engines_cleanup_common - cleans up the engine state created by
- *                                the common initiailizers.
+ *                                the common initializers.
  * @engine: Engine to cleanup.
  *
  * This cleans up everything created by the common helpers.
@@ -865,6 +865,63 @@ void intel_engine_cancel_stop_cs(struct intel_engine_cs *engine)
 		      _MASKED_BIT_DISABLE(STOP_RING));
 }
 
+static i915_reg_t get_idle_poll_reg(const struct intel_engine_cs *engine)
+{
+	if (engine->id != RCS)
+		return INVALID_MMIO_REG;
+
+	if (IS_GEN(engine->i915, 9))
+		return GEN9_RCS_FE_FSM2;
+
+	if (IS_GEN(engine->i915, 8))
+		return GEN6_RCS_PWR_FSM;
+
+	return INVALID_MMIO_REG;
+}
+
+static void disable_idle_messaging(struct intel_engine_cs *engine)
+{
+	struct drm_i915_private *dev_priv = engine->i915;
+	i915_reg_t poll_reg;
+
+	poll_reg = get_idle_poll_reg(engine);
+	if (!i915_mmio_reg_valid(poll_reg))
+		return;
+
+	GEM_DEBUG_WARN_ON(I915_READ_FW(GEN6_RC_SLEEP_PSMI_CONTROL) &
+			  GEN6_PSMI_SLEEP_MSG_DISABLE);
+	/*
+	 * Hardware must not be in middle of idle flow signalling
+	 * when the RING_CTL is zeroed. In order to prevent this
+	 * we disable the messaging temporarily.
+	 */
+	I915_WRITE_FW(GEN6_RC_SLEEP_PSMI_CONTROL,
+		      _MASKED_BIT_ENABLE(GEN6_PSMI_SLEEP_MSG_DISABLE));
+
+	/*
+	 * Poll the magic bits to ensure that engine state machine
+	 * is in valid state for stopping the ring.
+	 */
+	if (__intel_wait_for_register_fw(dev_priv, poll_reg,
+					 0x7f, 0x30,
+					 5000, 0,
+					 NULL))
+		DRM_DEBUG_DRIVER("psmi idle msg poll timeout\n");
+}
+
+static void enable_idle_messaging(struct intel_engine_cs *engine)
+{
+	struct drm_i915_private *dev_priv = engine->i915;
+	i915_reg_t poll_reg;
+
+	poll_reg = get_idle_poll_reg(engine);
+	if (!i915_mmio_reg_valid(poll_reg))
+		return;
+
+	I915_WRITE_FW(GEN6_RC_SLEEP_PSMI_CONTROL,
+		      _MASKED_BIT_DISABLE(GEN6_PSMI_SLEEP_MSG_DISABLE));
+}
+
 int intel_engine_stop_ring(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
@@ -880,9 +937,14 @@ int intel_engine_stop_ring(struct intel_engine_cs *engine)
 	I915_WRITE_FW(RING_TAIL(base), 0);
 	POSTING_READ_FW(RING_TAIL(base));
 
+	/* Idle messaging needs to be off during ring disable */
+	disable_idle_messaging(engine);
+
 	/* The ring must be empty before it is disabled */
 	I915_WRITE_FW(RING_CTL(base), 0);
 
+	enable_idle_messaging(engine);
+
 	/* Check acts as a post */
 	if (I915_READ_FW(RING_HEAD(base))) {
 		GEM_TRACE("%s: ring head [%x] not parked\n",
-- 
2.17.1