sbsa_gwdt: Introduce a panic notifier

hulk inclusion
category: feature
bugzilla: NA
CVE: NA

When the kernel panic we reset the timeout to pretimeout, then after
pretimeout seconds the sbsa_gwdt reset the system.

The pretimeout to be set is configured via the watchdog-core, but the
meaning is different from that of the watchdog-core. The pretimeout here
defines the new timeout for the sbsa_gwdt after panic while that of the
watchdog-core is meaningful where the WDT would raise an interrupt
before timeout and it defines the length of that period. That period of
sbsa_gwdt cannot be changed separately so the redefination here doesn't
make trouble.

The pretimeout here follow the same limit of that of watchdog-core that
the pretimeout shall be smaller than timeout, since we prefer that the
sbsa_gwdt would reset the system sooner on panic.

We add a new kconfig ARM_SBSA_WATCHDOG_PANIC_NOTIFIER to control the
feature. Set action to 2 to enable the notifier.
Signed-off-by: NWang Wensheng <wangwensheng4@huawei.com>
Reviewed-by: NXiongfeng Wang <wangxiongfeng2@huawei.com>
Reviewed-by: NDing Tianhong <dingtianhong@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/watchdog/Kconfig

@@ -273,6 +273,14 @@ config ARM_SBSA_WATCHDOG
 	  To compile this driver as module, choose M here: The module
 	  will be called sbsa_gwdt.
 
+config ARM_SBSA_WATCHDOG_PANIC_NOTIFIER
+	bool "Reset the WDT Timeout on Panic"
+	depends on ASCEND_FEATURES
+	depends on ARM_SBSA_WATCHDOG
+	help
+	  This registers a panic notifier that reset the timeout of watchdog to
+	  pretimeout set by user before.
+
 config ASM9260_WATCHDOG
 	tristate "Alphascale ASM9260 watchdog"
 	depends on MACH_ASM9260 || COMPILE_TEST

drivers/watchdog/sbsa_gwdt.c

@@ -108,12 +108,13 @@ MODULE_PARM_DESC(timeout,
  * action refers to action taken when watchdog gets WS0
  * 0 = skip
  * 1 = panic
+ * 2 = panic and reset timeout (need to enable CONFIG_ARM_SBSA_WATCHDOG_PANIC_NOTIFIER)
  * defaults to skip (0)
  */
 static int action;
 module_param(action, int, 0);
 MODULE_PARM_DESC(action, "after watchdog gets WS0 interrupt, do: "
-		 "0 = skip(*)  1 = panic");
+		 "0 = skip(*)  1 = panic 2 = panic_notifier");
 
 static bool nowayout = WATCHDOG_NOWAYOUT;
 module_param(nowayout, bool, S_IRUGO);
@@ -130,6 +131,11 @@ static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd,
 	struct sbsa_gwdt *gwdt = watchdog_get_drvdata(wdd);
 
 	wdd->timeout = timeout;
+#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC_NOTIFIER
+	/* Disable pretimeout if it doesn't fit the new timeout */
+	if (action == 2 && wdd->pretimeout >= wdd->timeout)
+		wdd->pretimeout = 0;
+#endif
 
 	if (action)
 		writel(gwdt->clk * timeout,
@@ -208,7 +214,7 @@ static irqreturn_t sbsa_gwdt_interrupt(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-static const struct watchdog_info sbsa_gwdt_info = {
+static struct watchdog_info sbsa_gwdt_info = {
 	.identity	= WATCHDOG_NAME,
 	.options	= WDIOF_SETTIMEOUT |
 			  WDIOF_KEEPALIVEPING |
@@ -225,6 +231,44 @@ static const struct watchdog_ops sbsa_gwdt_ops = {
 	.get_timeleft	= sbsa_gwdt_get_timeleft,
 };
 
+#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC_NOTIFIER
+static struct sbsa_gwdt_notifier_s {
+	struct sbsa_gwdt	*gwdt;
+	struct notifier_block	panic_notifier;
+} sbsa_gwdt_notifier;
+
+static int gwdt_reset_timeout(struct notifier_block *self,
+			      unsigned long v, void *p)
+{
+	struct sbsa_gwdt *gwdt =
+		container_of(self, struct sbsa_gwdt_notifier_s,
+			     panic_notifier)->gwdt;
+	unsigned int timeout = gwdt->wdd.pretimeout;
+	unsigned int div = 1U;
+
+	/*
+	 * If the panic occurred after when WSO was raised, the gwdt would
+	 * reset the board after WOR. If WS0 was not raised WOR * 2 would
+	 * take before gwdt would reset the board.
+	 */
+	if (!(readl(gwdt->control_base + SBSA_GWDT_WCS) & SBSA_GWDT_WCS_WS0))
+		div = 2U;
+	writel(gwdt->clk * timeout / div, gwdt->control_base + SBSA_GWDT_WOR);
+
+	return 0;
+}
+
+static void sbsa_register_panic_notifier(struct sbsa_gwdt *gwdt)
+{
+	sbsa_gwdt_notifier.gwdt = gwdt;
+	sbsa_gwdt_notifier.panic_notifier.notifier_call = gwdt_reset_timeout;
+	sbsa_gwdt_notifier.panic_notifier.priority = INT_MAX;
+
+	atomic_notifier_chain_register(&panic_notifier_list,
+				       &sbsa_gwdt_notifier.panic_notifier);
+}
+#endif
+
 static int sbsa_gwdt_probe(struct platform_device *pdev)
 {
 	void __iomem *rf_base, *cf_base;
@@ -317,6 +361,20 @@ static int sbsa_gwdt_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+#ifdef CONFIG_ARM_SBSA_WATCHDOG_PANIC_NOTIFIER
+	if (action == 2) {
+		/*
+		 * Since pretimeout should be smaller than timeout we initialize
+		 * pretimeout to timeout-1.
+		 * Add WDIOF_PRETIMEOUT flags to enable user to configure it.
+		 */
+		gwdt->wdd.pretimeout = gwdt->wdd.timeout - 1;
+		sbsa_gwdt_info.options |= WDIOF_PRETIMEOUT;
+
+		sbsa_register_panic_notifier(gwdt);
+	}
+#endif
+
 	dev_info(dev, "Initialized with %ds timeout @ %u Hz, action=%d.%s\n",
 		 wdd->timeout, gwdt->clk, action,
 		 status & SBSA_GWDT_WCS_EN ? " [enabled]" : "");