[PATCH 3/3] watchdog: qcom: register a restart notifier

Josh Cartwright
2014-09-18T22:33:59Z

The WDT's BITE_TIME warm-reset behavior can be leveraged as a last
resort mechanism for triggering chip reset. Usually, other restart
methods (such as PS_HOLD) are preferrable for issuing a more complete
reset of the chip. As such, keep the priority of the watchdog notifier
low.

Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
---
drivers/watchdog/qcom-wdt.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index e9409f5..710ab43 100644
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -15,6 +15,7 @@
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
+#include <linux/reboot.h>
#include <linux/watchdog.h>

#define WDT_RST 0x0
@@ -24,6 +25,7 @@
struct qcom_wdt {
struct watchdog_device wdd;
unsigned long freq;
+ struct notifier_block restart_nb;
void __iomem *base;
};

@@ -82,6 +84,24 @@ static const struct watchdog_info qcom_wdt_info = {
.identity = KBUILD_MODNAME,
};

+static int qcom_wdt_restart(struct notifier_block *nb, unsigned long action,
+ void *data)
+{
+ struct qcom_wdt *wdt = container_of(nb, struct qcom_wdt, restart_nb);
+
+ /*
+ * Trigger watchdog bite:
+ * Setup BITE_TIME to be very low, and enable WDT.
+ */
+ mutex_lock(&wdt->wdd.lock);
+ writel_relaxed(0, wdt->base + WDT_EN);
+ writel_relaxed(1, wdt->base + WDT_RST);
+ writel_relaxed(0x31F3, wdt->base + WDT_BITE_TIME);
+ writel_relaxed(1, wdt->base + WDT_EN);
+ mutex_unlock(&wdt->wdd.lock);
+ return NOTIFY_DONE;
+}
+
static int qcom_watchdog_probe(struct platform_device *pdev)
{
struct qcom_wdt *wdt;
@@ -121,6 +141,17 @@ static int qcom_watchdog_probe(struct platform_device *pdev)
return ret;
}

+ /*
+ * WDT restart notifier has priority 0 (use as a last resort)
+ */
+ wdt->restart_nb.notifier_call = qcom_wdt_restart;
+ ret = register_restart_handler(&wdt->restart_nb);
+ if (ret) {
+ dev_err(&pdev->dev, "failed to setup restart handler\n");
+ watchdog_unregister_device(&wdt->wdd);
+ return ret;
+ }
+
return 0;
}