[PATCH v3 3/4] clocksource/drivers/timer-vt8500: Prepare for watchdog functionality

[Alexey Charkov <alchark@gmail.com>]

VIA/WonderMedia system timer can generate a watchdog reset when its
clocksource counter matches the value in the match register 0 and
watchdog function is enabled. For this to work, obvously the clock event
device must use a different match register (1~3) and respective interrupt.

Check if at least two interrupts are provided by the device tree, then use
match register 1 for system clock events and reserve match register 0 for
the watchdog. Instantiate a platform device for the watchdog and give it
access to the MMIO registers base of the timer through platform data.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
---
 drivers/clocksource/timer-vt8500.c | 68 +++++++++++++++++++++++++++++++++++---
 1 file changed, 63 insertions(+), 5 deletions(-)

diff --git a/drivers/clocksource/timer-vt8500.c b/drivers/clocksource/timer-vt8500.c
index 9f28f30dcaf83ab4e9c89952175b0d4c75bd6b40..122cc046140d5e9edff20ff41a49b4e62064dd40 100644
--- a/drivers/clocksource/timer-vt8500.c
+++ b/drivers/clocksource/timer-vt8500.c
@@ -21,6 +21,8 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
 
 #define VT8500_TIMER_OFFSET	0x0100
 #define VT8500_TIMER_HZ		3000000
@@ -55,6 +57,9 @@
 #define MIN_OSCR_DELTA		16
 
 static void __iomem *regbase;
+static unsigned int sys_timer_ch;	 /* which match register to use
+					  * for the system timer
+					  */
 
 static u64 vt8500_timer_read(struct clocksource *cs)
 {
@@ -81,15 +86,15 @@ static int vt8500_timer_set_next_event(unsigned long cycles,
 	int loops = msecs_to_loops(10);
 	u64 alarm = clocksource.read(&clocksource) + cycles;
 
-	while (readl(regbase + TIMER_ACC_STS_REG) & TIMER_ACC_WR_MATCH(0)
+	while (readl(regbase + TIMER_ACC_STS_REG) & TIMER_ACC_WR_MATCH(sys_timer_ch)
 	       && --loops)
 		cpu_relax();
-	writel((unsigned long)alarm, regbase + TIMER_MATCH_REG(0));
+	writel((unsigned long)alarm, regbase + TIMER_MATCH_REG(sys_timer_ch));
 
 	if ((signed)(alarm - clocksource.read(&clocksource)) <= MIN_OSCR_DELTA)
 		return -ETIME;
 
-	writel(TIMER_INT_EN_MATCH(0), regbase + TIMER_INT_EN_REG);
+	writel(TIMER_INT_EN_MATCH(sys_timer_ch), regbase + TIMER_INT_EN_REG);
 
 	return 0;
 }
@@ -131,7 +136,9 @@ static int __init vt8500_timer_init(struct device_node *np)
 		return -ENXIO;
 	}
 
-	timer_irq = irq_of_parse_and_map(np, 0);
+	sys_timer_ch = of_irq_count(np) > 1 ? 1 : 0;
+
+	timer_irq = irq_of_parse_and_map(np, sys_timer_ch);
 	if (!timer_irq) {
 		pr_err("%s: Missing irq description in Device Tree\n",
 								__func__);
@@ -140,7 +147,7 @@ static int __init vt8500_timer_init(struct device_node *np)
 
 	writel(TIMER_CTRL_ENABLE, regbase + TIMER_CTRL_REG);
 	writel(TIMER_STATUS_CLEARALL, regbase + TIMER_STATUS_REG);
-	writel(~0, regbase + TIMER_MATCH_REG(0));
+	writel(~0, regbase + TIMER_MATCH_REG(sys_timer_ch));
 
 	ret = clocksource_register_hz(&clocksource, VT8500_TIMER_HZ);
 	if (ret) {
@@ -166,4 +173,55 @@ static int __init vt8500_timer_init(struct device_node *np)
 	return 0;
 }
 
+/*
+ * This probe gets called after the timer is already up and running. This will create
+ * the watchdog device as a child since the registers are shared.
+ */
+static int vt8500_timer_probe(struct platform_device *pdev)
+{
+	struct platform_device *vt8500_watchdog_device;
+	struct device *dev = &pdev->dev;
+	int ret;
+
+	if (!sys_timer_ch) {
+		dev_info(dev, "Not enabling watchdog: only one irq was given");
+		return 0;
+	}
+
+	if (!regbase)
+		return dev_err_probe(dev, -ENOMEM,
+			"Timer not initialized, cannot create watchdog");
+
+	vt8500_watchdog_device = platform_device_alloc("vt8500-wdt", -1);
+	if (!vt8500_watchdog_device)
+		return dev_err_probe(dev, -ENOMEM,
+			"Failed to allocate vt8500-wdt");
+
+	/* Pass the base address as platform data and nothing else */
+	vt8500_watchdog_device->dev.platform_data = regbase;
+	vt8500_watchdog_device->dev.parent = dev;
+
+	ret = platform_device_add(vt8500_watchdog_device);
+	if (ret)
+		platform_device_put(vt8500_watchdog_device);
+
+	return ret;
+}
+
+static const struct of_device_id vt8500_timer_of_match[] = {
+	{ .compatible = "via,vt8500-timer", },
+	{},
+};
+
+static struct platform_driver vt8500_timer_driver = {
+	.probe  = vt8500_timer_probe,
+	.driver = {
+		.name = "vt8500-timer",
+		.of_match_table = vt8500_timer_of_match,
+		.suppress_bind_attrs = true,
+	},
+};
+
+builtin_platform_driver(vt8500_timer_driver);
+
 TIMER_OF_DECLARE(vt8500, "via,vt8500-timer", vt8500_timer_init);

-- 
2.49.0