From: Marc Zyngier <marc.zyngier@arm.com>
Date: Sat, 19 Aug 2017 10:16:02 +0100
Subject: irqchip/gic-v3-its: Properly handle command queue wrapping
Patch-mainline: v4.14-rc1
Git-commit: 9bdd8b1cdeb6a873acb1d1e915d372e3440a4179
References: FATE#323954

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>
Acked-by: Alexander Graf <agraf@suse.de>
---
 drivers/irqchip/irq-gic-v3-its.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -453,7 +453,13 @@
 
 	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--;