[RFC PATCH 4/4] ARM: dt: Add TWD bindings and driver support

[marc.zyngier@arm.com (Marc Zyngier)]

Add device tree support to the arm_smp_twd driver.

The DT bindings for the TWD are defined as such:
- one timer node per CPU, using corresponding PPI
  interrupt controller
- provides both timer and watchdog interrupt

Tested on RealView PB11MPCore and VExpress.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 Documentation/devicetree/bindings/arm/twd.txt |   54 ++++++++++++++
 drivers/clocksource/arm_smp_twd.c             |   92 +++++++++++++++++++++---
 2 files changed, 134 insertions(+), 12 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/arm/twd.txt

diff --git a/Documentation/devicetree/bindings/arm/twd.txt b/Documentation/devicetree/bindings/arm/twd.txt
new file mode 100644
index 0000000..3823a81
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/twd.txt
@@ -0,0 +1,54 @@
+* ARM Timer Watchdog
+
+ARM SMP cores are often associated with a TWD providing a per-cpu timer
+and a per-cpu watchdog. Usually wired to the PPI interface of a GIC.
+
+Main node properties:
+
+- compatible		: "arm,smp-twd", "localtimer"
+- reg			: register mapping for the registers.
+- #address-cells	: <1>
+- #size-cells		: <0>
+
+Timer sub nodes (one per CPU)
+
+- interrupt-parent	: phandle to the corresponding gic-ppi.
+- interrupts		: <IRQtimer IRQwatchdog> (usually <29 30>)
+- reg			: index of the CPU this timer is connected to.
+
+Example (ARM RealView PB11-MPCore):
+
+localtimer at 1f000600 {
+	compatible = "arm,smp-twd", "localtimer";
+	reg = <0x1f000600 0x100>;
+	#address-cells = <1>;
+	#size-cells = <0>;
+
+	/*
+	 * One timer per CPU, bound to the corresponding
+	 * PPI interface.
+	 */
+	timer at 0 {
+		interrupt-parent = <&gic0ppi0>;
+		interrupts = <29 30>;
+		reg = <0>;
+	};
+
+	timer at 1 {
+		interrupt-parent = <&gic0ppi1>;
+		interrupts = <29 30>;
+		reg = <1>;
+	};
+
+	timer at 2 {
+		interrupt-parent = <&gic0ppi2>;
+		interrupts = <29 30>;
+		reg = <2>;
+	};
+
+	timer at 3 {
+		interrupt-parent = <&gic0ppi3>;
+		interrupts = <29 30>;
+		reg = <3>;
+	};
+};
diff --git a/drivers/clocksource/arm_smp_twd.c b/drivers/clocksource/arm_smp_twd.c
index 65f4669..586acad 100644
--- a/drivers/clocksource/arm_smp_twd.c
+++ b/drivers/clocksource/arm_smp_twd.c
@@ -19,6 +19,9 @@
 #include <linux/interrupt.h>
 #include <linux/ioport.h>
 #include <linux/platform_device.h>
+#include <linux/of_platform.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
 #include <linux/clk.h>
 #include <linux/cpufreq.h>
 #include <linux/err.h>
@@ -37,11 +40,11 @@
 #define TWD_TIMER_CONTROL_IT_ENABLE	(1 << 2)
 
 static void __iomem *twd_base;
-static int twd_ppi;
 
 static struct clk *twd_clk;
 static unsigned long twd_timer_rate;
 static DEFINE_PER_CPU(bool, irq_reqd);
+static DEFINE_PER_CPU(int, twd_irq);
 static struct clock_event_device __percpu *twd_evt;
 
 static void twd_set_mode(enum clock_event_mode mode,
@@ -223,7 +226,7 @@ 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->irq = gic_ppi_to_vppi(twd_ppi);
+	clk->irq = __get_cpu_var(twd_irq);
 	clk->cpumask = cpumask_of(smp_processor_id());
 
 	pr_debug("Configuring %s on cpu #%d\n", clk->name, smp_processor_id());
@@ -290,31 +293,90 @@ static struct notifier_block __cpuinitdata twd_cpu_nb = {
 	.notifier_call = twd_cpu_notify,
 };
 
-static int twd_probe(struct platform_device *pdev)
+#ifdef CONFIG_OF
+static struct device_node *twd_get_timer_node(struct device_node *twd_np,
+					      struct device_node *child,
+					      int *timer_nr)
+{
+	child = of_get_next_child(twd_np, child);
+	if (child) {
+		const __be32 *reg;
+		reg = of_get_property(child, "reg", NULL);
+		if (!reg)
+			*timer_nr = -1;
+		else
+			*timer_nr = be32_to_cpu(*reg);
+	}
+
+	return child;
+}
+
+static int __devinit twd_of_probe_irq(struct platform_device *pdev)
+{
+	struct device_node *timer = NULL;
+	int timer_nr;
+
+	if (!pdev->dev.of_node)
+		return -1;
+
+	while((timer = twd_get_timer_node(pdev->dev.of_node,
+					  timer, &timer_nr))) {
+		if (timer_nr < 0 || timer_nr >= NR_CPUS) {
+			dev_info(&pdev->dev, "Unknown timer id %d\n", timer_nr);
+			continue;
+		}
+
+		per_cpu(twd_irq, timer_nr) = irq_of_parse_and_map(timer, 0);
+		pr_info("%s IRQ%d", timer->full_name, per_cpu(twd_irq, timer_nr));
+	}
+
+	return 0;
+}
+#else
+static int __devinit twd_of_probe_irq(struct platform_device *pdev)
+{
+	return -1;
+}
+#endif
+
+static int __devinit twd_probe(struct platform_device *pdev)
 {
 	struct resource *mem;
 	struct clock_event_device *clk;
-	int irq;
 
 	if (twd_base)
 		return -EBUSY;
 
 	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	irq = platform_get_irq(pdev, 0);
-	if (!mem || irq < 0)
+	if (!mem)
 		return -EINVAL;
+	twd_base = ioremap(mem->start, resource_size(mem));
+
+	if (!twd_base)
+		return -ENOMEM;
+
+	if (twd_of_probe_irq(pdev)) {
+		int irq;
+		int i;
 
-	twd_base	= ioremap(mem->start, resource_size(mem));
-	twd_evt		= alloc_percpu(struct clock_event_device);
-	if (!twd_base || !twd_evt) {
+		irq = platform_get_irq(pdev, 0);
+		if (irq < 0) {
+			iounmap(twd_base);
+			return -EINVAL;
+		}
+
+		for (i = 0; i < NR_CPUS; i++)
+			per_cpu(twd_irq, i) = gic_ppi_to_cpu_vppi(irq, i);
+	}
+
+	twd_evt	= alloc_percpu(struct clock_event_device);
+	if (!twd_evt) {
 		iounmap(twd_base);
 		twd_base = NULL;
 		free_percpu(twd_evt);
 		return -ENOMEM;
 	}
 
-	twd_ppi = irq;
-
 	/* Immediately configure the timer on the boot CPU */
 	clk = per_cpu_ptr(twd_evt, smp_processor_id());
 	twd_setup(clk);
@@ -329,11 +391,17 @@ static int twd_remove(struct platform_device *pdev)
 	return -EBUSY;
 }
 
+static const struct of_device_id twd_of_ids[] = {
+	{ .compatible	= "arm,smp-twd" },
+	{ },
+};
+
 static struct platform_driver twd_driver = {
 	.probe	= twd_probe,
 	.remove = __devexit_p(twd_remove),
 	.driver = {
-		.name	= "arm_smp_twd",
+		.name		= "arm_smp_twd",
+		.of_match_table	= twd_of_ids,
 	},
 };
 
-- 
1.7.0.4