From 5b644c7a218702668d7b610994e7dcbc3d4705d3 Mon Sep 17 00:00:00 2001
From: Magnus Damm <damm@igel.co.jp>
Date: Tue, 28 Apr 2009 08:17:54 +0000
Subject: clocksource: improve sh_cmt clocksource overflow handling

This patch improves the sh_cmt clocksource handling.

Currently the counter value is ignored in the case of
overflow. With this patch the overflow flag is read
before and after reading the counter, removing any
counter value and overflow flag mismatch issues.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

diff --git a/drivers/clocksource/sh_cmt.c b/drivers/clocksource/sh_cmt.c
index c247564..d607ac2 100644
--- a/drivers/clocksource/sh_cmt.c
+++ b/drivers/clocksource/sh_cmt.c
@@ -111,16 +111,21 @@ static unsigned long sh_cmt_get_counter(struct sh_cmt_priv *p,
 					int *has_wrapped)
 {
 	unsigned long v1, v2, v3;
+	int o1, o2;
+
+	o1 = sh_cmt_read(p, CMCSR) & p->overflow_bit;
 
 	/* Make sure the timer value is stable. Stolen from acpi_pm.c */
 	do {
+		o2 = o1;
 		v1 = sh_cmt_read(p, CMCNT);
 		v2 = sh_cmt_read(p, CMCNT);
 		v3 = sh_cmt_read(p, CMCNT);
-	} while (unlikely((v1 > v2 && v1 < v3) || (v2 > v3 && v2 < v1)
-			  || (v3 > v1 && v3 < v2)));
+		o1 = sh_cmt_read(p, CMCSR) & p->overflow_bit;
+	} while (unlikely((o1 != o2) || (v1 > v2 && v1 < v3)
+			  || (v2 > v3 && v2 < v1) || (v3 > v1 && v3 < v2)));
 
-	*has_wrapped = sh_cmt_read(p, CMCSR) & p->overflow_bit;
+	*has_wrapped = o1;
 	return v2;
 }
 
@@ -394,7 +399,7 @@ static cycle_t sh_cmt_clocksource_read(struct clocksource *cs)
 	raw = sh_cmt_get_counter(p, &has_wrapped);
 
 	if (unlikely(has_wrapped))
-		raw = p->match_value;
+		raw += p->match_value;
 	spin_unlock_irqrestore(&p->lock, flags);
 
 	return value + raw;
-- 
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