re: [PATCH 3/3] mailbox: pcc: Fix command timeout due to missed interrupt

 
+	/*
+	 * Set chan_in_use before ringing the doorbell so a fast completion
+	 * interrupt is not mistaken for a shared interrupt from another
+	 * subspace. Use WRITE_ONCE() for the lockless flag update. The
+	 * ordered MMIO accessor used to ring the doorbell keeps this store
+	 * visible before the platform is notified.
+	 */
+	if (pchan->plat_irq > 0)
+		WRITE_ONCE(pchan->chan_in_use, true);
 	ret = pcc_chan_reg_read_modify_write(&pchan->db);
 	if (!ret && pchan->plat_irq > 0)
-		pchan->chan_in_use = true;
+		WRITE_ONCE(pchan->chan_in_use, false);
 
 	return ret;
 }
-- 
2.43.0
iAt the end of the above code, 
 WRITE_ONCE(pchan->chan_in_use, false); 
 should be 
 WRITE_ONCE(pchan->chan_in_use, true);

In order to keep the original semantics.  The flag is cleared when the messages is ACKed, not here.  This version causes a hang.