[Intel-gfx] [PATCH v2] drm/i915/pxp: don't start pxp without mei_pxp bind

[Juston Li]

pxp will not start correctly until after mei_pxp bind completes and
intel_pxp_init_hw() is called.

This fixes a race condition during bootup where we observed a small
window for pxp commands to be sent before mei_pxp bind completed.

Changes since v1:
- check pxp_component instead of pxp_component_added (Daniele)
- pxp_component needs tee_mutex (Daniele)
- return -EAGAIN so caller knows to retry (Daniele)

Signed-off-by: Juston Li <justonli at google.com>
---
 drivers/gpu/drm/i915/pxp/intel_pxp.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.c b/drivers/gpu/drm/i915/pxp/intel_pxp.c
index 15311eaed848..8b395ebc430a 100644
--- a/drivers/gpu/drm/i915/pxp/intel_pxp.c
+++ b/drivers/gpu/drm/i915/pxp/intel_pxp.c
@@ -187,6 +187,14 @@ int intel_pxp_start(struct intel_pxp *pxp)
 	if (!intel_pxp_is_enabled(pxp))
 		return -ENODEV;
 
+	mutex_lock(&pxp->tee_mutex);
+	/* check if mei_pxp is bound */
+	if (!pxp->pxp_component) {
+		mutex_unlock(&pxp->tee_mutex);
+		return -EAGAIN;
+	}
+	mutex_unlock(&pxp->tee_mutex);
+
 	mutex_lock(&pxp->arb_mutex);
 
 	if (pxp->arb_is_valid)
-- 
2.37.1.559.g78731f0fdb-goog