ARM: architected timers: add DT support

Add runtime DT support and documentation for the Cortex A7/A15
architected timers.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

Documentation/devicetree/bindings/arm/arch_timer.txt

+* ARM architected timer
+
+ARM Cortex-A7 and Cortex-A15 have a per-core architected timer, which
+provides per-cpu timers.
+
+The timer is attached to a GIC to deliver its per-processor interrupts.
+
+** Timer node properties:
+
+- compatible : Should at least contain "arm,armv7-timer".
+
+- interrupts : Interrupt list for secure, non-secure, virtual and
+  hypervisor timers, in that order.
+
+- clock-frequency : The frequency of the main counter, in Hz. Optional.
+
+Example:
+
+	timer {
+		compatible = "arm,cortex-a15-timer",
+			     "arm,armv7-timer";
+		interrupts = <1 13 0xf08>,
+			     <1 14 0xf08>,
+			     <1 11 0xf08>,
+			     <1 10 0xf08>;
+		clock-frequency = <100000000>;
+	};

arch/arm/include/asm/arch_timer.h

@@ -10,12 +10,18 @@ struct arch_timer {
 #ifdef CONFIG_ARM_ARCH_TIMER
 int arch_timer_register(struct arch_timer *);
 int arch_timer_sched_clock_init(void);
+int arch_timer_of_register(void);
 #else
 static inline int arch_timer_register(struct arch_timer *at)
 {
 	return -ENXIO;
 }
 
+static inline int arch_timer_of_register(void)
+{
+	return -ENXIO;
+}
+
 static inline int arch_timer_sched_clock_init(void)
 {
 	return -ENXIO;

arch/arm/kernel/arch_timer.c

@@ -17,6 +17,7 @@
 #include <linux/jiffies.h>
 #include <linux/clockchips.h>
 #include <linux/interrupt.h>
+#include <linux/of_irq.h>
 #include <linux/io.h>
 
 #include <asm/cputype.h>
@@ -245,13 +246,10 @@ static struct local_timer_ops arch_timer_ops __cpuinitdata = {
 	.stop	= arch_timer_stop,
 };
 
-int __init arch_timer_register(struct arch_timer *at)
+static int __init arch_timer_common_register(void)
 {
 	int err;
 
-	if (at->res[0].start <= 0 || !(at->res[0].flags & IORESOURCE_IRQ))
-		return -EINVAL;
-
 	err = arch_timer_available();
 	if (err)
 		return err;
@@ -262,7 +260,6 @@ int __init arch_timer_register(struct arch_timer *at)
 
 	clocksource_register_hz(&clocksource_counter, arch_timer_rate);
 
-	arch_timer_ppi = at->res[0].start;
 	err = request_percpu_irq(arch_timer_ppi, arch_timer_handler,
 				 "arch_timer", arch_timer_evt);
 	if (err) {
@@ -271,8 +268,7 @@ int __init arch_timer_register(struct arch_timer *at)
 		goto out_free;
 	}
 
-	if (at->res[1].start > 0 || (at->res[1].flags & IORESOURCE_IRQ)) {
-		arch_timer_ppi2 = at->res[1].start;
+	if (arch_timer_ppi2) {
 		err = request_percpu_irq(arch_timer_ppi2, arch_timer_handler,
 					 "arch_timer", arch_timer_evt);
 		if (err) {
@@ -300,6 +296,49 @@ int __init arch_timer_register(struct arch_timer *at)
 	return err;
 }
 
+int __init arch_timer_register(struct arch_timer *at)
+{
+	if (at->res[0].start <= 0 || !(at->res[0].flags & IORESOURCE_IRQ))
+		return -EINVAL;
+
+	arch_timer_ppi = at->res[0].start;
+
+	if (at->res[1].start > 0 || (at->res[1].flags & IORESOURCE_IRQ))
+		arch_timer_ppi2 = at->res[1].start;
+
+	return arch_timer_common_register();
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id arch_timer_of_match[] __initconst = {
+	{ .compatible	= "arm,armv7-timer",	},
+	{},
+};
+
+int __init arch_timer_of_register(void)
+{
+	struct device_node *np;
+	u32 freq;
+
+	np = of_find_matching_node(NULL, arch_timer_of_match);
+	if (!np) {
+		pr_err("arch_timer: can't find DT node\n");
+		return -ENODEV;
+	}
+
+	/* Try to determine the frequency from the device tree or CNTFRQ */
+	if (!of_property_read_u32(np, "clock-frequency", &freq))
+		arch_timer_rate = freq;
+
+	arch_timer_ppi = irq_of_parse_and_map(np, 0);
+	arch_timer_ppi2 = irq_of_parse_and_map(np, 1);
+	pr_info("arch_timer: found %s irqs %d %d\n",
+		np->name, arch_timer_ppi, arch_timer_ppi2);
+
+	return arch_timer_common_register();
+}
+#endif
+
 int __init arch_timer_sched_clock_init(void)
 {
 	int err;