clocksource/arm_smp_twd: handle frequency changes

index 5e2e8cc..a18ac0d 100644
@@ -19,6 +19,10 @@
 #include <linux/interrupt.h>
 #include <linux/ioport.h>
 #include <linux/platform_device.h>
+#include <linux/clk.h>
+#include <linux/cpufreq.h
+#include <linux/err.h>
+#include <linux/percpu.h>
 
 #include <asm/hardware/gic.h>
 

@@ -35,6 +39,8 @@
 static void __iomem *twd_base;
 static int twd_ppi;
 
+static struct clk *twd_clk;
+static DEFINE_PER_CPU(struct clock_event_device *, twd_ce);
 static unsigned long twd_timer_rate;
 static DEFINE_PER_CPU(bool, irq_reqd);
 static struct clock_event_device __percpu *twd_evt;

@@ -90,6 +96,52 @@ static irqreturn_t twd_handler(int irq, void *dev_id)
 	return IRQ_NONE;
 }
 
+#ifdef CONFIG_CPU_FREQ
+
+/*
+ * Updates clockevent frequency when the cpu frequency changes.
+ * Called on the cpu that is changing frequency with interrupts disabled.
+ */
+static void twd_update_frequency(void *data)
+{
+	twd_timer_rate = clk_get_rate(twd_clk);
+
+	clockevents_update_freq(__get_cpu_var(twd_ce), twd_timer_rate);
+}
+
+static int twd_cpufreq_transition(struct notifier_block *nb,
+	unsigned long state, void *data)
+{
+	struct cpufreq_freqs *freqs = data;
+
+	/*
+	 * The twd clock events must be reprogrammed to account for the new
+	 * frequency.  The timer is local to a cpu, so cross-call to the
+	 * changing cpu.
+	 */
+	if (state == CPUFREQ_POSTCHANGE || state == CPUFREQ_RESUMECHANGE)
+		smp_call_function_single(freqs->cpu, twd_update_frequency,
+			NULL, 1);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block twd_cpufreq_nb = {
+	.notifier_call = twd_cpufreq_transition,
+};
+
+static int twd_cpufreq_init(void)
+{
+	if (!IS_ERR_OR_NULL(twd_clk))
+		return cpufreq_register_notifier(&twd_cpufreq_nb,
+			CPUFREQ_TRANSITION_NOTIFIER);
+
+	return 0;
+}
+core_initcall(twd_cpufreq_init);
+
+#endif
+
 static void __cpuinit twd_calibrate_rate(void)
 {
 	unsigned long count;

@@ -129,6 +181,27 @@ static void __cpuinit twd_calibrate_rate(void)
 	}
 }
 
+static struct clk *twd_get_clock(void)
+{
+	struct clk *clk;
+	int err;
+
+	clk = clk_get_sys("smp_twd", NULL);
+	if (IS_ERR(clk)) {
+		pr_err("smp_twd: clock not found: %d\n", (int)PTR_ERR(clk));
+		return clk;
+	}
+
+	err = clk_enable(clk);
+	if (err) {
+		pr_err("smp_twd: clock failed to enable: %d\n", err);
+		clk_put(clk);
+		return ERR_PTR(err);
+	}
+
+	return clk;
+}
+
 /*
  * Setup the local clock events for a CPU.
  */

@@ -137,7 +210,13 @@ static void __cpuinit twd_setup(void *data)
 	struct clock_event_device *clk = data;
 	int err;
 
-	twd_calibrate_rate();
+	if (!twd_clk)
+		twd_clk = twd_get_clock();
+
+	if (!IS_ERR_OR_NULL(twd_clk))
+		twd_timer_rate = clk_get_rate(twd_clk);
+	else
+		twd_calibrate_rate();
 
 	clk->name = "arm_smp_twd";
 	clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |

@@ -145,10 +224,6 @@ static void __cpuinit twd_setup(void *data)
 	clk->rating = 450;
 	clk->set_mode = twd_set_mode;
 	clk->set_next_event = twd_set_next_event;
-	clk->shift = 20;
-	clk->mult = div_sc(twd_timer_rate, NSEC_PER_SEC, clk->shift);
-	clk->max_delta_ns = clockevent_delta2ns(0xffffffff, clk);
-	clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 	clk->irq = gic_ppi_to_vppi(twd_ppi);
 	clk->cpumask = cpumask_of(smp_processor_id());
 

@@ -163,7 +238,9 @@ static void __cpuinit twd_setup(void *data)
 		return;
 	}
 
-	clockevents_register_device(clk);
+	__get_cpu_var(twd_ce) = clk;
+	clockevents_config_and_register(clk, twd_timer_rate,
+					0xf, 0xffffffff);
 }
 
 static void __cpuinit twd_teardown(void *data)