linux-kernel - [PATCH] x86: clean up hpet timer reinit

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Date:	Fri, 6 Feb 2009 15:09:43 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Pavel Emelyanov <xemul@...nvz.org>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kirill Korotaev <dev@...nvz.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH] x86: clean up hpet timer reinit


* Pavel Emelyanov <xemul@...nvz.org> wrote:

> Sorry for late response - took some time to re-check this...

Applied to tip:timers/urgent, thanks Pavel!

Note, since i've already queued up the minimal fix i've created a delta 
cleanup patch from your v2 patch - see it below. (It is the exact same end 
result in terms of code, just a nicer splitup.)

	Ingo

------------------->
>From ff08f76d738d0ec0f334b187f61e160caa321d54 Mon Sep 17 00:00:00 2001
From: Pavel Emelyanov <xemul@...nvz.org>
Date: Wed, 4 Feb 2009 13:40:31 +0300
Subject: [PATCH] x86: clean up hpet timer reinit

Implement Linus's suggestion: introduce the hpet_cnt_ahead()
helper function to compare hpet time values - like other
wrapping counter comparisons are abstracted away elsewhere.
(jiffies, ktime_t, etc.)

Reported-by: Kirill Korotaev <dev@...nvz.org>
Signed-off-by: Pavel Emelyanov <xemul@...nvz.org>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 arch/x86/kernel/hpet.c |   12 ++++++++++--
 1 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index c761f91..388254f 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -897,7 +897,7 @@ static unsigned long hpet_rtc_flags;
 static int hpet_prev_update_sec;
 static struct rtc_time hpet_alarm_time;
 static unsigned long hpet_pie_count;
-static unsigned long hpet_t1_cmp;
+static u32 hpet_t1_cmp;
 static unsigned long hpet_default_delta;
 static unsigned long hpet_pie_delta;
 static unsigned long hpet_pie_limit;
@@ -905,6 +905,14 @@ static unsigned long hpet_pie_limit;
 static rtc_irq_handler irq_handler;
 
 /*
+ * Check that the hpet counter c1 is ahead of the c2
+ */
+static inline int hpet_cnt_ahead(u32 c1, u32 c2)
+{
+	return (s32)(c2 - c1) < 0;
+}
+
+/*
  * Registers a IRQ handler.
  */
 int hpet_register_irq_handler(rtc_irq_handler handler)
@@ -1075,7 +1083,7 @@ static void hpet_rtc_timer_reinit(void)
 		hpet_t1_cmp += delta;
 		hpet_writel(hpet_t1_cmp, HPET_T1_CMP);
 		lost_ints++;
-	} while ((s32)(hpet_readl(HPET_COUNTER) - hpet_t1_cmp) > 0);
+	} while (!hpet_cnt_ahead(hpet_t1_cmp, hpet_readl(HPET_COUNTER)));
 
 	if (lost_ints) {
 		if (hpet_rtc_flags & RTC_PIE)
--
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