drm/i915/pxp: don't start pxp without mei_pxp bind

pxp will not start correctly until after mei_pxp bind completes and
intel_pxp_init_hw() is called.
Wait for the bind to complete before proceeding with startup.

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

Changes since v2:
- wait for pxp_component to bind instead of returning -EAGAIN (Daniele)

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@chromium.org>
Reviewed-by: Andrzej Hajda <andrzej.hajda@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220818174205.2412730-1-justonli@chromium.org

drivers/gpu/drm/i915/pxp/intel_pxp.c

@@ -176,6 +176,18 @@ static void pxp_queue_termination(struct intel_pxp *pxp)
 	spin_unlock_irq(&gt->irq_lock);
 }
 
+static bool pxp_component_bound(struct intel_pxp *pxp)
+{
+	bool bound = false;
+
+	mutex_lock(&pxp->tee_mutex);
+	if (pxp->pxp_component)
+		bound = true;
+	mutex_unlock(&pxp->tee_mutex);
+
+	return bound;
+}
+
 /*
  * the arb session is restarted from the irq work when we receive the
  * termination completion interrupt
@@ -187,6 +199,9 @@ int intel_pxp_start(struct intel_pxp *pxp)
 	if (!intel_pxp_is_enabled(pxp))
 		return -ENODEV;
 
+	if (wait_for(pxp_component_bound(pxp), 250))
+		return -ENXIO;
+
 	mutex_lock(&pxp->arb_mutex);
 
 	if (pxp->arb_is_valid)