irqchip/gic-v3-its: Properly handle command queue wrapping

Marc Zyngier · Marc Zyngier · commit 9bdd8b1cdeb6 · 2017-08-19T10:16:02.000+01:00
wait_for_range_completion() is nicely busted when handling
wrapping of the command queue, leading to an early exit
instead of waiting for the command to have been executed.

Fortunately, the impact is pretty minor, as it only impair
the detection of an ITS that doesn't make any forward progress
for a whole second. And an ITS should *never* lock up.

Reported-by: Yang Yingliang &lt;yangyingliang@huawei.com&gt;
Signed-off-by: Marc Zyngier &lt;marc.zyngier@arm.com&gt;
diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
@@ -453,7 +453,13 @@ static void its_wait_for_range_completion(struct its_node *its,
 
 	while (1) {
 		rd_idx = readl_relaxed(its->base + GITS_CREADR);
-		if (rd_idx >= to_idx || rd_idx < from_idx)
+
+		/* Direct case */
+		if (from_idx < to_idx && rd_idx >= to_idx)
+			break;
+
+		/* Wrapped case */
+		if (from_idx >= to_idx && rd_idx >= to_idx && rd_idx < from_idx)
 			break;
 
 		count--;
