[Intel-gfx] [PATCH] drm/i915/guc: Prevent ggtt->invalidate assert during GuC reload

[Michel Thierry]

The driver reloads the GuC firmware after full gpu reset or
suspend/resume, but it never disables the GuC beforehand.
This leads us to hit the assert inside i915_ggtt_enable_guc added
by commit 04f7b24eccdf ("drm/i915/guc: Assert that we switch between
known ggtt->invalidate functions").

As a workaround, don't call i915_ggtt_enable_guc if there is a GuC
execbuf_client; because if there isn't one we are either loading in a
fresh system or we called intel_uc_fini_hw.

I'm inclined to this approach because even if intel_uc_fini_hw could be
added to the suspend path, we will still need to keep this for the
full gpu reset case.

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski at intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
Signed-off-by: Michel Thierry <michel.thierry at intel.com>
---
 drivers/gpu/drm/i915/intel_uc.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_uc.c b/drivers/gpu/drm/i915/intel_uc.c
index a8930f2feacf..564b0d2b8842 100644
--- a/drivers/gpu/drm/i915/intel_uc.c
+++ b/drivers/gpu/drm/i915/intel_uc.c
@@ -339,8 +339,14 @@ int intel_uc_init_hw(struct drm_i915_private *dev_priv)
 	guc_disable_communication(guc);
 	gen9_reset_guc_interrupts(dev_priv);
 
-	/* We need to notify the guc whenever we change the GGTT */
-	i915_ggtt_enable_guc(dev_priv);
+	/*
+	 * We need to notify the guc whenever we change the GGTT; but if we
+	 * are reloading the firmware (after full gpu reset or suspend/resume),
+	 * we should skip this since gtt->invalidate was already set (or we hit
+	 * an assert).
+	 */
+	if (!dev_priv->guc.execbuf_client)
+		i915_ggtt_enable_guc(dev_priv);
 
 	if (i915.enable_guc_submission) {
 		/*
-- 
2.11.0