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

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 <yangyingliang@huawei.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 6893287..350a959 100644 (file)
--- 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--;