ARM: AT91: Add DT support to AT91RM9200 System Timer

Based on AT91 PIT DT patch from Jean-Christophe PLAGNIOL-VILLARD.
Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>

Documentation/devicetree/bindings/arm/atmel-at91.txt

@@ -7,6 +7,12 @@ PIT Timer required properties:
 - interrupts: Should contain interrupt for the PIT which is the IRQ line
   shared across all System Controller members.
 
+System Timer (ST) required properties:
+- compatible: Should be "atmel,at91rm9200-st"
+- reg: Should contain registers location and length
+- interrupts: Should contain interrupt for the ST which is the IRQ line
+  shared across all System Controller members.
+
 TC/TCLIB Timer required properties:
 - compatible: Should be "atmel,<chip>-pit".
   <chip> can be "at91rm9200" or "at91sam9x5"

arch/arm/mach-at91/at91rm9200_time.c

@@ -24,6 +24,9 @@
 #include <linux/irq.h>
 #include <linux/clockchips.h>
 #include <linux/export.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
 
 #include <asm/mach/time.h>
 
@@ -91,7 +94,8 @@ static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
 static struct irqaction at91rm9200_timer_irq = {
 	.name		= "at91_tick",
 	.flags		= IRQF_SHARED | IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
-	.handler	= at91rm9200_timer_interrupt
+	.handler	= at91rm9200_timer_interrupt,
+	.irq		= NR_IRQS_LEGACY + AT91_ID_SYS,
 };
 
 static cycle_t read_clk32k(struct clocksource *cs)
@@ -179,8 +183,60 @@ static struct clock_event_device clkevt = {
 void __iomem *at91_st_base;
 EXPORT_SYMBOL_GPL(at91_st_base);
 
+#ifdef CONFIG_OF
+static struct of_device_id at91rm9200_st_timer_ids[] = {
+	{ .compatible = "atmel,at91rm9200-st" },
+	{ /* sentinel */ }
+};
+
+static int __init of_at91rm9200_st_init(void)
+{
+	struct device_node *np;
+	int ret;
+
+	np = of_find_matching_node(NULL, at91rm9200_st_timer_ids);
+	if (!np)
+		goto err;
+
+	at91_st_base = of_iomap(np, 0);
+	if (!at91_st_base)
+		goto node_err;
+
+	/* Get the interrupts property */
+	ret = irq_of_parse_and_map(np, 0);
+	if (!ret)
+		goto ioremap_err;
+	at91rm9200_timer_irq.irq = ret;
+
+	of_node_put(np);
+
+	return 0;
+
+ioremap_err:
+	iounmap(at91_st_base);
+node_err:
+	of_node_put(np);
+err:
+	return -EINVAL;
+}
+#else
+static int __init of_at91rm9200_st_init(void)
+{
+	return -EINVAL;
+}
+#endif
+
 void __init at91rm9200_ioremap_st(u32 addr)
 {
+#ifdef CONFIG_OF
+	struct device_node *np;
+
+	np = of_find_matching_node(NULL, at91rm9200_st_timer_ids);
+	if (np) {
+		of_node_put(np);
+		return;
+	}
+#endif
 	at91_st_base = ioremap(addr, 256);
 	if (!at91_st_base)
 		panic("Impossible to ioremap ST\n");
@@ -191,13 +247,16 @@ void __init at91rm9200_ioremap_st(u32 addr)
  */
 void __init at91rm9200_timer_init(void)
 {
+	/* For device tree enabled device: initialize here */
+	of_at91rm9200_st_init();
+
 	/* Disable all timer interrupts, and clear any pending ones */
 	at91_st_write(AT91_ST_IDR,
 		AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS);
 	at91_st_read(AT91_ST_SR);
 
 	/* Make IRQs happen for the system timer */
-	setup_irq(NR_IRQS_LEGACY + AT91_ID_SYS, &at91rm9200_timer_irq);
+	setup_irq(at91rm9200_timer_irq.irq, &at91rm9200_timer_irq);
 
 	/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
 	 * directly for the clocksource and all clockevents, after adjusting