[ARM] 2862/1: VST aka CONFIG_NO_IDLE_HZ support for PXA2xx

Patch from Nicolas Pitre

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

2 files changed, 53 insertions, 2 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4bf0e8737e1f..dc0fafc7f9bd 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -365,8 +365,8 @@ config NO_IDLE_HZ
 
           Please note that dynamic tick may affect the accuracy of
           timekeeping on some platforms depending on the implementation.
-          Currently at least OMAP platform is known to have accurate
-          timekeeping with dynamic tick.
+          Currently at least OMAP and PXA2xx platforms are known to have
+          accurate timekeeping with dynamic tick.
 
 config ARCH_DISCONTIGMEM_ENABLE
         bool
diff --git a/arch/arm/mach-pxa/time.c b/arch/arm/mach-pxa/time.c
index 6e5202154f91..72b15e9a373a 100644
--- a/arch/arm/mach-pxa/time.c
+++ b/arch/arm/mach-pxa/time.c
@@ -70,6 +70,11 @@ static unsigned long pxa_gettimeoffset (void)
         return usec;
 }
 
+#ifdef CONFIG_NO_IDLE_HZ
+static unsigned long initial_match;
+static int match_posponed;
+#endif
+
 static irqreturn_t
 pxa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
@@ -77,6 +82,13 @@ pxa_timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 
         write_seqlock(&xtime_lock);
 
+#ifdef CONFIG_NO_IDLE_HZ
+        if (match_posponed) {
+                match_posponed = 0;
+                OSMR0 = initial_match;
+        }
+#endif
+
         /* Loop until we get ahead of the free running timer.
          * This ensures an exact clock tick count and time accuracy.
          * IRQs are disabled inside the loop to ensure coherence between
@@ -126,6 +138,42 @@ static void __init pxa_timer_init(void)
         OSCR = 0;               /* initialize free-running timer, force first match */
 }
 
+#ifdef CONFIG_NO_IDLE_HZ
+static int pxa_dyn_tick_enable_disable(void)
+{
+        /* nothing to do */
+        return 0;
+}
+
+static void pxa_dyn_tick_reprogram(unsigned long ticks)
+{
+        if (ticks > 1) {
+                initial_match = OSMR0;
+                OSMR0 = initial_match + ticks * LATCH;
+                match_posponed = 1;
+        }
+}
+
+static irqreturn_t
+pxa_dyn_tick_handler(int irq, void *dev_id, struct pt_regs *regs)
+{
+        if (match_posponed) {
+                match_posponed = 0;
+                OSMR0 = initial_match;
+                if ( (signed long)(initial_match - OSCR) <= 8 )
+                        return pxa_timer_interrupt(irq, dev_id, regs);
+        }
+        return IRQ_NONE;
+}
+
+static struct dyn_tick_timer pxa_dyn_tick = {
+        .enable         = pxa_dyn_tick_enable_disable,
+        .disable        = pxa_dyn_tick_enable_disable,
+        .reprogram      = pxa_dyn_tick_reprogram,
+        .handler        = pxa_dyn_tick_handler,
+};
+#endif
+
 #ifdef CONFIG_PM
 static unsigned long osmr[4], oier;
 
@@ -161,4 +209,7 @@ struct sys_timer pxa_timer = {
         .suspend        = pxa_timer_suspend,
         .resume         = pxa_timer_resume,
         .offset         = pxa_gettimeoffset,
+#ifdef CONFIG_NO_IDLE_HZ
+        .dyn_tick       = &pxa_dyn_tick,
+#endif
 };