watchdog: qcom: register a restart notifier

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>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index 68db322341bc8a093edc344d3cd572d050fbba84..aa85618c4d0328bf42e8ca43157f9c67451ceee9 100644 (file)
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -11,11 +11,13 @@
  *
  */
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #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
@@ -26,6 +28,7 @@ struct qcom_wdt {
        struct watchdog_device  wdd;
        struct clk              *clk;
        unsigned long           rate;
+       struct notifier_block   restart_nb;
        void __iomem            *base;
 };
 
@@ -84,6 +87,32 @@ 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);
+       u32 timeout;
+
+       /*
+        * Trigger watchdog bite:
+        *    Setup BITE_TIME to be 128ms, and enable WDT.
+        */
+       timeout = 128 * wdt->rate / 1000;
+
+       writel(0, wdt->base + WDT_EN);
+       writel(1, wdt->base + WDT_RST);
+       writel(timeout, wdt->base + WDT_BITE_TIME);
+       writel(1, wdt->base + WDT_EN);
+
+       /*
+        * Actually make sure the above sequence hits hardware before sleeping.
+        */
+       wmb();
+
+       msleep(150);
+       return NOTIFY_DONE;
+}
+
 static int qcom_wdt_probe(struct platform_device *pdev)
 {
        struct qcom_wdt *wdt;
@@ -147,6 +176,14 @@ static int qcom_wdt_probe(struct platform_device *pdev)
                goto err_clk_unprepare;
        }
 
+       /*
+        * 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");
+
        platform_set_drvdata(pdev, wdt);
        return 0;
 
@@ -159,6 +196,7 @@ static int qcom_wdt_remove(struct platform_device *pdev)
 {
        struct qcom_wdt *wdt = platform_get_drvdata(pdev);
 
+       unregister_restart_handler(&wdt->restart_nb);
        watchdog_unregister_device(&wdt->wdd);
        clk_disable_unprepare(wdt->clk);
        return 0;