Merge branch linux-tegra-2.6.36 into android-tegra-2.6.36

Change-Id: Iec42f1fa234c03c6267f91ba0553d1c651b9ba94

1 files changed, 76 insertions, 34 deletions

diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 014862ae170c..3dc62ee45639 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -17,6 +17,7 @@
 #include <linux/clockchips.h>
 #include <linux/irq.h>
 #include <linux/io.h>
+#include <linux/cpufreq.h>
 
 #include <asm/smp_twd.h>
 #include <asm/hardware/gic.h>
@@ -26,7 +27,7 @@ void __iomem *twd_base;
 
 static unsigned long twd_timer_rate;
 static unsigned long twd_periphclk_prescaler;
-static unsigned long twd_target_rate;
+static unsigned long twd_cpu_rate;
 
 static void twd_set_mode(enum clock_event_mode mode,
 			struct clock_event_device *clk)
@@ -82,7 +83,13 @@ int twd_timer_ack(void)
 	return 0;
 }
 
-void twd_recalc_prescaler(unsigned long new_rate)
+/*
+ * Recalculate the twd prescaler value when the cpu frequency changes. To
+ * prevent early timer interrupts, must be called before changing the cpu
+ * frequency if the frequency is increasing, or after if the frequency is
+ * decreasing.
+ */
+static void twd_update_prescaler(void *data)
 {
 	u32 ctrl;
 	int prescaler;
@@ -90,7 +97,7 @@ void twd_recalc_prescaler(unsigned long new_rate)
 
 	BUG_ON(twd_periphclk_prescaler == 0 || twd_timer_rate == 0);
 
-	periphclk_rate = new_rate / twd_periphclk_prescaler;
+	periphclk_rate = twd_cpu_rate / twd_periphclk_prescaler;
 
 	prescaler = DIV_ROUND_UP(periphclk_rate, twd_timer_rate);
 	prescaler = clamp(prescaler - 1, 0, 0xFF);
@@ -101,60 +108,95 @@ void twd_recalc_prescaler(unsigned long new_rate)
 	__raw_writel(ctrl, twd_base + TWD_TIMER_CONTROL);
 }
 
+static int twd_cpufreq_transition(struct notifier_block *nb,
+	unsigned long state, void *data)
+{
+	struct cpufreq_freqs *freqs = data;
+	if (((freqs->new > freqs->old) && state == CPUFREQ_PRECHANGE) ||
+	    ((freqs->old > freqs->new) && state == CPUFREQ_POSTCHANGE)) {
+		/* freqs->new is in kHz, twd_cpu_rate is in Hz */
+		twd_cpu_rate = freqs->new * 1000;
+
+		smp_call_function_single(freqs->cpu, twd_update_prescaler,
+			NULL, 1);
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block twd_cpufreq_nb = {
+	.notifier_call = twd_cpufreq_transition,
+};
+
+static int twd_cpufreq_init(void)
+{
+	if (twd_cpu_rate)
+		return cpufreq_register_notifier(&twd_cpufreq_nb,
+			CPUFREQ_TRANSITION_NOTIFIER);
+
+	return 0;
+}
+core_initcall(twd_cpufreq_init);
+
 static void __cpuinit twd_calibrate_rate(unsigned long target_rate,
 	unsigned int periphclk_prescaler)
 {
 	unsigned long load, count;
 	u64 waitjiffies;
-	unsigned long cpu_rate;
 
 	/*
 	 * If this is the first time round, we need to work out how fast
 	 * the timer ticks
 	 */
-	printk(KERN_INFO "Calibrating local timer... ");
+	if (twd_timer_rate == 0) {
+		printk(KERN_INFO "Calibrating local timer... ");
 
-	/* Wait for a tick to start */
-	waitjiffies = get_jiffies_64() + 1;
+		/* Wait for a tick to start */
+		waitjiffies = get_jiffies_64() + 1;
 
-	while (get_jiffies_64() < waitjiffies)
-		udelay(10);
+		while (get_jiffies_64() < waitjiffies)
+			udelay(10);
 
-	/* OK, now the tick has started, let's get the timer going */
-	waitjiffies += 5;
+		/* OK, now the tick has started, let's get the timer going */
+		waitjiffies += 5;
 
-			 /* enable, no interrupt or reload */
-	__raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
+				 /* enable, no interrupt or reload */
+		__raw_writel(0x1, twd_base + TWD_TIMER_CONTROL);
 
-			 /* maximum value */
-	__raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
+				 /* maximum value */
+		__raw_writel(0xFFFFFFFFU, twd_base + TWD_TIMER_COUNTER);
 
-	while (get_jiffies_64() < waitjiffies)
-		udelay(10);
+		while (get_jiffies_64() < waitjiffies)
+			udelay(10);
 
-	count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
+		count = __raw_readl(twd_base + TWD_TIMER_COUNTER);
 
-	twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
+		twd_timer_rate = (0xFFFFFFFFU - count) * (HZ / 5);
 
-	/*
-	 * If a target rate has been requested, adjust the TWD prescaler
-	 * to get the closest lower frequency.
-	 */
-	if (target_rate) {
-		twd_periphclk_prescaler = periphclk_prescaler;
-		twd_target_rate = target_rate;
+		/*
+		 * If a target rate has been requested, adjust the TWD prescaler
+		 * to get the closest lower frequency.
+		 */
+		if (target_rate) {
+			twd_periphclk_prescaler = periphclk_prescaler;
 
-		printk("%lu.%02luMHz, setting to ",
-			twd_timer_rate / 1000000,
+			printk("%lu.%02luMHz, setting to ",
+				twd_timer_rate / 1000000,
+				(twd_timer_rate / 10000) % 100);
+			twd_cpu_rate = twd_timer_rate * periphclk_prescaler;
+			twd_timer_rate = target_rate;
+			twd_update_prescaler(NULL);
+		}
+
+		printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
 			(twd_timer_rate / 10000) % 100);
-		cpu_rate = twd_timer_rate * periphclk_prescaler;
-		twd_timer_rate = twd_target_rate;
-		twd_recalc_prescaler(cpu_rate);
+	} else {
+		if (target_rate) {
+			BUG_ON(target_rate != twd_timer_rate);
+			twd_update_prescaler(NULL);
+		}
 	}
 
-	printk("%lu.%02luMHz.\n", twd_timer_rate / 1000000,
-		(twd_timer_rate / 10000) % 100);
-
 	load = twd_timer_rate / HZ;
 
 	__raw_writel(load, twd_base + TWD_TIMER_LOAD);