[RFC PATCH 1/4] watchdog: at91sam9_wdt: better watchdog support

[Boris BREZILLON]

The at91sam9 watchdog timer cannot configured twice, and the current
implementation only tries to configure in a static way:
- 2 seconds timeout
- wdt restart every 500ms

If the timer has already been configured with different values, it returns an
error and do not create any watchdog device.

This is not critical if the watchdog is disabled, but if it has been enabled with
different timeout values it will lead to a SoC reset.

This patch series tries to address this issue by adapting the heartbeat value
according the WDT timer config:
- it first tries to configure the timer as requested.
- if it fails it fallbacks to the current config, adapting its heartbeat timer
to the needs

This patch series also move to a dynamically allocated at91wdt device instead
of the static instance.

It adds a new at91 wdt type: software. This new type make use of the at91 wdt
interrupt to trigger a software watchdog.

Finally it adds several properties to the device tree bindings.

Signed-off-by: Boris BREZILLON <b.brezillon@xxxxxxxxxxx>
---
 drivers/watchdog/at91sam9_wdt.c |  319 +++++++++++++++++++++++++++++----------
 1 file changed, 236 insertions(+), 83 deletions(-)

diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
index be37dde..fb47ec5 100644
--- a/drivers/watchdog/at91sam9_wdt.c
+++ b/drivers/watchdog/at91sam9_wdt.c
@@ -19,11 +19,13 @@
 
 #include <linux/errno.h>
 #include <linux/init.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/platform_device.h>
+#include <linux/reboot.h>
 #include <linux/types.h>
 #include <linux/watchdog.h>
 #include <linux/jiffies.h>
@@ -31,23 +33,32 @@
 #include <linux/bitops.h>
 #include <linux/uaccess.h>
 #include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
 
 #include "at91sam9_wdt.h"
 
 #define DRV_NAME "AT91SAM9 Watchdog"
 
-#define wdt_read(field) \
-	__raw_readl(at91wdt_private.base + field)
-#define wdt_write(field, val) \
-	__raw_writel((val), at91wdt_private.base + field)
+#define wdt_read(wdt, field) \
+	__raw_readl((wdt)->base + field)
+#define wdt_write(wtd, field, val) \
+	__raw_writel((val), (wdt)->base + field)
 
 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
  * use this to convert a watchdog
  * value from/to milliseconds.
  */
+#define hz_to_ticks(h)  (((h << 8) / HZ) - 1)
+#define ticks_to_hz(t)	(((t + 1) * HZ) >> 8)
 #define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
 #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
 
+#define WDT_MR_RESET	0x3FFF2FFF
+
+#define WDT_WDD_MAX	0xFFF
+#define WDT_WDV_MAX	0xFFF
+
 /* Hardware timeout in seconds */
 #define WDT_HW_TIMEOUT 2
 
@@ -66,23 +77,41 @@ module_param(nowayout, bool, 0);
 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
 	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 
-static struct watchdog_device at91_wdt_dev;
-static void at91_ping(unsigned long data);
-
-static struct {
+#define to_wdt(wdd) container_of(wdd, struct at91wdt, wdd)
+struct at91wdt {
+	struct watchdog_device wdd;
 	void __iomem *base;
 	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
 	struct timer_list timer;	/* The timer that pings the watchdog */
-} at91wdt_private;
+	u32 mr;
+	u32 mr_mask;
+	unsigned long heartbeat;	/* WDT heartbeat in jiffies */
+	bool nowayout;
+	unsigned int irq;
+};
 
 /* ......................................................................... */
 
+static irqreturn_t wdt_interrupt(int irq, void *dev_id)
+{
+	struct at91wdt *wdt = (struct at91wdt *)dev_id;
+
+	if (wdt_read(wdt, AT91_WDT_SR)) {
+		/* Reboot */
+		pr_crit("at91sam9 WDT software reset\n");
+		emergency_restart();
+		pr_crit("Reboot didn't ?????\n");
+	}
+
+	return IRQ_HANDLED;
+}
+
 /*
  * Reload the watchdog timer.  (ie, pat the watchdog)
  */
-static inline void at91_wdt_reset(void)
+static inline void at91_wdt_reset(struct at91wdt *wdt)
 {
-	wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
+	wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
 }
 
 /*
@@ -90,26 +119,20 @@ static inline void at91_wdt_reset(void)
  */
 static void at91_ping(unsigned long data)
 {
-	if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
-	    (!watchdog_active(&at91_wdt_dev))) {
-		at91_wdt_reset();
-		mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
+	struct at91wdt *wdt = (struct at91wdt *)data;
+	if (time_before(jiffies, wdt->next_heartbeat) ||
+	    (!watchdog_active(&wdt->wdd))) {
+		at91_wdt_reset(wdt);
+		mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
 	} else
 		pr_crit("I will reset your machine !\n");
 }
 
 static int at91_wdt_ping(struct watchdog_device *wdd)
 {
+	struct at91wdt *wdt = to_wdt(wdd);
 	/* calculate when the next userspace timeout will be */
-	at91wdt_private.next_heartbeat = jiffies + wdd->timeout * HZ;
-	return 0;
-}
-
-static int at91_wdt_start(struct watchdog_device *wdd)
-{
-	/* calculate the next userspace timeout and modify the timer */
-	at91_wdt_ping(wdd);
-	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
+	wdt->next_heartbeat = jiffies + wdd->timeout * HZ;
 	return 0;
 }
 
@@ -125,36 +148,82 @@ static int at91_wdt_set_timeout(struct watchdog_device *wdd, unsigned int new_ti
 	return 0;
 }
 
-/*
- * Set the watchdog time interval in 1/256Hz (write-once)
- * Counter is 12 bit.
- */
-static int at91_wdt_settimeout(unsigned int timeout)
+static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt)
 {
-	unsigned int reg;
-	unsigned int mr;
-
-	/* Check if disabled */
-	mr = wdt_read(AT91_WDT_MR);
-	if (mr & AT91_WDT_WDDIS) {
-		pr_err("sorry, watchdog is disabled\n");
-		return -EIO;
+	u32 tmp;
+	u32 delta;
+	u32 value;
+	int err;
+	u32 mask = wdt->mr_mask;
+
+	tmp = wdt_read(wdt, AT91_WDT_MR);
+	if ((tmp & mask) != (wdt->mr & mask)) {
+		if (tmp == WDT_MR_RESET) {
+			wdt_write(wdt, AT91_WDT_MR, wdt->mr);
+			tmp = wdt_read(wdt, AT91_WDT_MR);
+		}
+	}
+
+	if (tmp & AT91_WDT_WDDIS) {
+		if (wdt->mr & AT91_WDT_WDDIS)
+			return 0;
+		dev_err(wdt->wdd.parent,
+			": sorry, watchdog is disabled\n");
+		return -EINVAL;
+	}
+
+	value = tmp & AT91_WDT_WDV;
+	delta = (tmp & AT91_WDT_WDD) >> 16;
+
+	if (delta < value) {
+		if ((value / (value - delta)) < 4) {
+			dev_err(wdt->wdd.parent,
+				": sorry, max-heartbeat should be at least 4 times min-heartbeat (max-heartbeat = %d x min-heartbeat)\n",
+				(value / (value - delta)));
+			return -EINVAL;
+		}
+	}
+
+	wdt->heartbeat = ticks_to_hz(value / 4);
+
+	if (!wdt->heartbeat) {
+		dev_err(wdt->wdd.parent,
+			": sorry, linux timer (%i Hz) cannot handle watchdog timeout (%i ms)\n",
+			HZ, ticks_to_ms(value));
+		return -EINVAL;
+	}
+
+	if ((tmp & AT91_WDT_WDFIEN) && wdt->irq) {
+		err = request_irq(wdt->irq, wdt_interrupt,
+				  IRQF_SHARED | IRQF_IRQPOLL,
+				  pdev->name, wdt);
+		if (err)
+			return err;
 	}
 
-	/*
-	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
-	 *
-	 * Since WDV is a 12-bit counter, the maximum period is
-	 * 4096 / 256 = 16 seconds.
-	 */
-	reg = AT91_WDT_WDRSTEN	/* causes watchdog reset */
-		/* | AT91_WDT_WDRPROC	causes processor reset only */
-		| AT91_WDT_WDDBGHLT	/* disabled in debug mode */
-		| AT91_WDT_WDD		/* restart at any time */
-		| (timeout & AT91_WDT_WDV);  /* timer value */
-	wdt_write(AT91_WDT_MR, reg);
+	if ((tmp & wdt->mr_mask) != (wdt->mr & wdt->mr_mask))
+		dev_warn(wdt->wdd.parent,
+			 ": watchdog already configured differently (mr = %x expecting %x)\n",
+			 tmp & wdt->mr_mask, wdt->mr & wdt->mr_mask);
+
+	setup_timer(&wdt->timer, at91_ping, (unsigned long)wdt);
+	mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
+
+	/* Try to set timeout from device tree first */
+	if (watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev))
+		watchdog_init_timeout(&wdt->wdd, heartbeat, &pdev->dev);
+	watchdog_set_nowayout(&wdt->wdd, wdt->nowayout);
+	err = watchdog_register_device(&wdt->wdd);
+	if (err)
+		goto out_stop_timer;
+
+	wdt->next_heartbeat = jiffies + wdt->wdd.timeout * HZ;
 
 	return 0;
+
+out_stop_timer:
+	del_timer(&wdt->timer);
+	return err;
 }
 
 /* ......................................................................... */
@@ -167,63 +236,147 @@ static const struct watchdog_info at91_wdt_info = {
 
 static const struct watchdog_ops at91_wdt_ops = {
 	.owner =	THIS_MODULE,
-	.start =	at91_wdt_start,
+	.start =	at91_wdt_ping,
 	.stop =		at91_wdt_stop,
 	.ping =		at91_wdt_ping,
 	.set_timeout =	at91_wdt_set_timeout,
 };
 
-static struct watchdog_device at91_wdt_dev = {
-	.info =		&at91_wdt_info,
-	.ops =		&at91_wdt_ops,
-	.timeout =	WDT_HEARTBEAT,
-	.min_timeout =	1,
-	.max_timeout =	0xFFFF,
-};
+#if defined(CONFIG_OF)
+static int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
+{
+	u32 min = 0;
+	u32 max = 0xFFF;
+	const char *tmp;
+
+	wdt->base = of_iomap(np, 0);
+	if (!wdt->base) {
+		dev_err(wdt->wdd.parent, "failed to map registers, aborting.\n");
+		return -EINVAL;
+	}
+
+	/* Get the interrupts property */
+	wdt->irq = irq_of_parse_and_map(np, 0);
+	if (!wdt->irq)
+		dev_warn(wdt->wdd.parent, "failed to get IRQ from DT.\n");
+
+	if (!of_property_read_u32_index(np, "atmel,max-heartbeat-sec", 0,
+					&max)) {
+		max *= 256;
+		if (max > WDT_WDV_MAX)
+			max = WDT_WDV_MAX;
+
+		if (!of_property_read_u32_index(np, "atmel,min-heartbeat-sec",
+						0, &min)) {
+			min *= 256;
+			if (4 * min > max)
+				min = max / 4;
+		}
+	}
+
+	wdt->mr_mask = 0x3FFFFFFF;
+	wdt->mr = 0;
+	if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
+	    !strcmp(tmp, "software")) {
+		wdt->mr |= AT91_WDT_WDFIEN;
+		wdt->mr_mask &= ~AT91_WDT_WDRPROC;
+	} else
+		wdt->mr |= AT91_WDT_WDRSTEN;
+
+	if (!of_property_read_string(np, "atmel,reset-type", &tmp) &&
+	    !strcmp(tmp, "proc"))
+		wdt->mr |= AT91_WDT_WDRPROC;
+
+	if (of_property_read_bool(np, "atmel,disable")) {
+		wdt->mr |= AT91_WDT_WDDIS;
+		wdt->mr_mask &= AT91_WDT_WDDIS;
+	}
+
+	if (of_property_read_bool(np, "atmel,idle-halt"))
+		wdt->mr |= AT91_WDT_WDIDLEHLT;
+
+	if (of_property_read_bool(np, "atmel,dbg-halt"))
+		wdt->mr |= AT91_WDT_WDDBGHLT;
+
+	wdt->mr |= max | ((max - min) << 16);
+
+	return 0;
+}
+#else
+static inline int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
+{
+	return 0;
+}
+#endif
 
 static int __init at91wdt_probe(struct platform_device *pdev)
 {
 	struct resource	*r;
-	int res;
-
-	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
-	if (!r)
-		return -ENODEV;
-	at91wdt_private.base = ioremap(r->start, resource_size(r));
-	if (!at91wdt_private.base) {
-		dev_err(&pdev->dev, "failed to map registers, aborting.\n");
-		return -ENOMEM;
-	}
+	int err;
+	struct at91wdt *wdt;
 
-	at91_wdt_dev.parent = &pdev->dev;
-	watchdog_init_timeout(&at91_wdt_dev, heartbeat, &pdev->dev);
-	watchdog_set_nowayout(&at91_wdt_dev, nowayout);
+	wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+	if (!wdt)
+		return -ENOMEM;
 
-	/* Set watchdog */
-	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
-	if (res)
-		return res;
+	wdt->mr = (WDT_HW_TIMEOUT * 256) | AT91_WDT_WDRSTEN | AT91_WDT_WDD |
+		  AT91_WDT_WDDBGHLT | AT91_WDT_WDIDLEHLT;
+	wdt->mr_mask = 0x3FFFFFFF;
+	wdt->nowayout = nowayout;
+	wdt->wdd.parent = &pdev->dev;
+	wdt->wdd.info = &at91_wdt_info;
+	wdt->wdd.ops = &at91_wdt_ops;
+	wdt->wdd.timeout = WDT_HEARTBEAT;
+	wdt->wdd.min_timeout = 1;
+	wdt->wdd.max_timeout = 0xFFFF;
+
+	if (pdev->dev.of_node) {
+		err = of_at91wdt_init(pdev->dev.of_node, wdt);
+		if (err)
+			goto out_free_watchdog;
+	} else {
+		r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+		if (!r) {
+			err = -ENODEV;
+			goto out_free_watchdog;
+		}
+
+		wdt->base = ioremap(r->start, resource_size(r));
+		if (!wdt->base) {
+			dev_err(&pdev->dev, "failed to map registers, aborting.\n");
+			err = -ENOMEM;
+			goto out_free_watchdog;
+		}
+	}
 
-	res = watchdog_register_device(&at91_wdt_dev);
-	if (res)
-		return res;
+	err = at91_wdt_init(pdev, wdt);
+	if (err)
+		goto out_iounmap;
 
-	at91wdt_private.next_heartbeat = jiffies + at91_wdt_dev.timeout * HZ;
-	setup_timer(&at91wdt_private.timer, at91_ping, 0);
-	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
+	platform_set_drvdata(pdev, wdt);
 
 	pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
-		at91_wdt_dev.timeout, nowayout);
+		wdt->wdd.timeout, wdt->nowayout);
 
 	return 0;
+
+out_iounmap:
+	iounmap(wdt->base);
+out_free_watchdog:
+	devm_kfree(&pdev->dev, wdt);
+	return err;
 }
 
 static int __exit at91wdt_remove(struct platform_device *pdev)
 {
-	watchdog_unregister_device(&at91_wdt_dev);
+	struct at91wdt *wdt = platform_get_drvdata(pdev);
+	watchdog_unregister_device(&wdt->wdd);
 
 	pr_warn("I quit now, hardware will probably reboot!\n");
-	del_timer(&at91wdt_private.timer);
+	del_timer(&wdt->timer);
+
+	iounmap(wdt->base);
+	devm_kfree(&pdev->dev, wdt);
 
 	return 0;
 }
-- 
1.7.9.5

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