[ARM] pxa: Don't wind OSCR backwards over suspend/resume

OSCR is supposed to monotonically increment; however restoring it
to a time prior to OSMR0 may result in it being wound backwards.
Instead, if OSMR0 is within the minimum expiry time, wind OSMR0
forwards.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 12 insertions, 9 deletions

diff --git a/arch/arm/mach-pxa/time.c b/arch/arm/mach-pxa/time.c
index 3c4abbf31803..ac0bbad35238 100644
--- a/arch/arm/mach-pxa/time.c
+++ b/arch/arm/mach-pxa/time.c
@@ -181,7 +181,7 @@ static void __init pxa_timer_init(void)
 }
 
 #ifdef CONFIG_PM
-static unsigned long osmr[4], oier;
+static unsigned long osmr[4], oier, oscr;
 
 static void pxa_timer_suspend(void)
 {
@@ -190,23 +190,26 @@ static void pxa_timer_suspend(void)
         osmr[2] = OSMR2;
         osmr[3] = OSMR3;
         oier = OIER;
+        oscr = OSCR;
 }
 
 static void pxa_timer_resume(void)
 {
+        /*
+         * Ensure that we have at least MIN_OSCR_DELTA between match
+         * register 0 and the OSCR, to guarantee that we will receive
+         * the one-shot timer interrupt.  We adjust OSMR0 in preference
+         * to OSCR to guarantee that OSCR is monotonically incrementing.
+         */
+        if (osmr[0] - oscr < MIN_OSCR_DELTA)
+                osmr[0] += MIN_OSCR_DELTA;
+
         OSMR0 = osmr[0];
         OSMR1 = osmr[1];
         OSMR2 = osmr[2];
         OSMR3 = osmr[3];
         OIER = oier;
-
-        /*
-         * OSCR0 is the system timer, which has to increase
-         * monotonically until it rolls over in hardware.  The value
-         * (OSMR0 - LATCH) is OSCR0 at the most recent system tick,
-         * which is a handy value to restore to OSCR0.
-         */
-        OSCR = OSMR0 - LATCH;
+        OSCR = oscr;
 }
 #else
 #define pxa_timer_suspend NULL