From: Ulrich Obergfell <uobergfe@redhat.com>
Date: Wed, 1 Sep 2010 16:23:32 -0400
Subject: [time] introduce 'pmtimer_fine_grained' kernel parameter
Message-id: <1618040470.683941283358212941.JavaMail.root@zmail07.collab.prod.int.phx2.redhat.com>
Patchwork-id: 27994
O-Subject: [RHEL5.6 PATCH 1/3 BZ586285] introduce 'pmtimer_fine_grained'
	kernel parameter
Bugzilla: 586285
RH-Acked-by: Glauber Costa <glommer@redhat.com>

RH-Bugzilla: 586285
RH-Upstream-status: N/A

This is the second part of a four-part message. Please refer to first part:
http://post-office.corp.redhat.com/archives/rhkernel-list/2010-September/msg00037.html

Patch part 1 of 3
-----------------

Signed-off-by: Jarod Wilson <jarod@redhat.com>

diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
index ed86e23..f953710 100644
--- a/arch/x86_64/kernel/time.c
+++ b/arch/x86_64/kernel/time.c
@@ -103,6 +103,10 @@ struct timezone __sys_tz __section_sys_tz;
 
 /* -1=>disabled, 0=>autoconfigure, 1=>enabled */
 int timekeeping_use_tsc;
+
+/* 0=>disabled, 1=>enabled (default) */
+static unsigned int pmtimer_fine_grained = 1;
+
 static cycles_t cycles_per_tick, cycles_accounted_limit;
 
 /*
@@ -1941,3 +1945,29 @@ static int __init divider_setup(char *s)
 
 __setup("divider=", divider_setup);
 #endif
+
+
+/*
+ * If the kernel parameter 'divider' is set to a value greater than 1,
+ * the kernel parameter 'pmtimer_fine_grained' enables / disables the
+ * functionality of pmtimer_mark_offset_return_njiffies() as well as
+ * the divider-specific initialization of 'tick_nsec' in time_init().
+ */
+
+static int __init pmtimer_fine_grained_setup(char *s)
+{
+	unsigned int fine_grained = 1;
+	int ret = get_option(&s, (int *)&fine_grained);
+
+	if (ret == 1 && fine_grained < 2)
+		pmtimer_fine_grained = fine_grained;
+	else
+		printk(KERN_ERR "pmtimer_fine_grained: incorrect value\n");
+
+	if (!pmtimer_fine_grained)
+		printk(KERN_INFO "PM timer fine grained accounting disabled\n");
+
+	return 1;
+}
+
+__setup("pmtimer_fine_grained=", pmtimer_fine_grained_setup);