linux-kernel - [PATCH] clocksource: kona: avoid bogus warning

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Date:	Mon, 13 Jun 2016 22:40:36 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Florian Fainelli <f.fainelli@...il.com>,
	Ray Jui <rjui@...adcom.com>,
	Scott Branden <sbranden@...adcom.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	bcm-kernel-feedback-list@...adcom.com, linux-kernel@...r.kernel.org
Subject: [PATCH] clocksource: kona: avoid bogus warning

I could not figure out why, but gcc cannot prove that the
kona_timer_init function always initializes its two outputs,
and we get a warning for the use of the 'lsw' variable later,
which is obviously correct.

drivers/clocksource/bcm_kona_timer.c: In function 'kona_timer_init':
drivers/clocksource/bcm_kona_timer.c:119:13: error: 'lsw' may be used uninitialized in this function [-Werror=maybe-uninitialized]

Slightly reordering the loop makes the warning disappear, after
it becomes more obvious to the compiler that the loop is
always entered on the first iteration.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/clocksource/bcm_kona_timer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c
index 70d9c1e482dd..bbbfb03b46dd 100644
--- a/drivers/clocksource/bcm_kona_timer.c
+++ b/drivers/clocksource/bcm_kona_timer.c
@@ -69,7 +69,7 @@ static void kona_timer_disable_and_clear(void __iomem *base)
 static void
 kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
 {
-	int loop_limit = 4;
+	int loop_limit = 3;
 
 	/*
 	 * Read 64-bit free running counter
@@ -83,12 +83,12 @@ kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw)
 	 *      if new hi-word is equal to previously read hi-word then stop.
 	 */
 
-	while (--loop_limit) {
+	do {
 		*msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET);
 		*lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET);
 		if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET))
 			break;
-	}
+	} while (--loop_limit);
 	if (!loop_limit) {
 		pr_err("bcm_kona_timer: getting counter failed.\n");
 		pr_err(" Timer will be impacted\n");
-- 
2.7.0