remoteproc/omap: Add watchdog functionality for remote processors

Remote processors can be stuck in a loop, and may not be recoverable
if they do not have a built-in watchdog. The watchdog implementation
for OMAP remote processors uses external gptimers that can be used
to interrupt both the Linux host as well as the remote processor.

Each remote processor is responsible for refreshing the timer during
normal behavior - during OS task scheduling or entering the idle loop
properly. During a watchdog condition (executing a tight loop causing
no scheduling), the host processor gets interrupts and schedules a
recovery for the corresponding remote processor. The remote processor
may also get interrupted to be able to print a back trace.

A menuconfig option has also been added to enable/disable the Watchdog
functionality, with the default as disabled.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Andrew F. Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20200324110035.29907-15-t-kristo@ti.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/Kconfig

@@ -52,6 +52,18 @@ config OMAP_REMOTEPROC
 	  It's safe to say N here if you're not interested in multimedia
 	  offloading or just want a bare minimum kernel.
 
+config OMAP_REMOTEPROC_WATCHDOG
+	bool "OMAP remoteproc watchdog timer"
+	depends on OMAP_REMOTEPROC
+	default n
+	help
+	  Say Y here to enable watchdog timer for remote processors.
+
+	  This option controls the watchdog functionality for the remote
+	  processors in OMAP. Dedicated OMAP DMTimers are used by the remote
+	  processors and triggers the timer interrupt upon a watchdog
+	  detection.
+
 config WKUP_M3_RPROC
 	tristate "AMx3xx Wakeup M3 remoteproc support"
 	depends on SOC_AM33XX || SOC_AM43XX

drivers/remoteproc/omap_remoteproc.c

@@ -24,6 +24,7 @@
 #include <linux/platform_device.h>
 #include <linux/pm_runtime.h>
 #include <linux/dma-mapping.h>
+#include <linux/interrupt.h>
 #include <linux/remoteproc.h>
 #include <linux/mailbox_client.h>
 #include <linux/omap-iommu.h>
@@ -72,10 +73,12 @@ struct omap_rproc_mem {
  * struct omap_rproc_timer - data structure for a timer used by a omap rproc
  * @odt: timer pointer
  * @timer_ops: OMAP dmtimer ops for @odt timer
+ * @irq: timer irq
  */
 struct omap_rproc_timer {
 	struct omap_dm_timer *odt;
 	const struct omap_dm_timer_ops *timer_ops;
+	int irq;
 };
 
 /**
@@ -86,6 +89,7 @@ struct omap_rproc_timer {
  * @mem: internal memory regions data
  * @num_mems: number of internal memory regions
  * @num_timers: number of rproc timer(s)
+ * @num_wd_timers: number of rproc watchdog timers
  * @timers: timer(s) info used by rproc
  * @autosuspend_delay: auto-suspend delay value to be used for runtime pm
  * @need_resume: if true a resume is needed in the system resume callback
@@ -102,6 +106,7 @@ struct omap_rproc {
 	struct omap_rproc_mem *mem;
 	int num_mems;
 	int num_timers;
+	int num_wd_timers;
 	struct omap_rproc_timer *timers;
 	int autosuspend_delay;
 	bool need_resume;
@@ -219,6 +224,79 @@ static inline int omap_rproc_release_timer(struct omap_rproc_timer *timer)
 	return timer->timer_ops->free(timer->odt);
 }
 
+/**
+ * omap_rproc_get_timer_irq() - get the irq for a timer
+ * @timer: handle to a OMAP rproc timer
+ *
+ * This function is used to get the irq associated with a watchdog timer. The
+ * function is called by the OMAP remoteproc driver to register a interrupt
+ * handler to handle watchdog events on the remote processor.
+ *
+ * Return: irq id on success, otherwise a failure as returned by DMTimer ops
+ */
+static inline int omap_rproc_get_timer_irq(struct omap_rproc_timer *timer)
+{
+	return timer->timer_ops->get_irq(timer->odt);
+}
+
+/**
+ * omap_rproc_ack_timer_irq() - acknowledge a timer irq
+ * @timer: handle to a OMAP rproc timer
+ *
+ * This function is used to clear the irq associated with a watchdog timer. The
+ * The function is called by the OMAP remoteproc upon a watchdog event on the
+ * remote processor to clear the interrupt status of the watchdog timer.
+ */
+static inline void omap_rproc_ack_timer_irq(struct omap_rproc_timer *timer)
+{
+	timer->timer_ops->write_status(timer->odt, OMAP_TIMER_INT_OVERFLOW);
+}
+
+/**
+ * omap_rproc_watchdog_isr() - Watchdog ISR handler for remoteproc device
+ * @irq: IRQ number associated with a watchdog timer
+ * @data: IRQ handler data
+ *
+ * This ISR routine executes the required necessary low-level code to
+ * acknowledge a watchdog timer interrupt. There can be multiple watchdog
+ * timers associated with a rproc (like IPUs which have 2 watchdog timers,
+ * one per Cortex M3/M4 core), so a lookup has to be performed to identify
+ * the timer to acknowledge its interrupt.
+ *
+ * The function also invokes rproc_report_crash to report the watchdog event
+ * to the remoteproc driver core, to trigger a recovery.
+ *
+ * Return: IRQ_HANDLED on success, otherwise IRQ_NONE
+ */
+static irqreturn_t omap_rproc_watchdog_isr(int irq, void *data)
+{
+	struct rproc *rproc = data;
+	struct omap_rproc *oproc = rproc->priv;
+	struct device *dev = rproc->dev.parent;
+	struct omap_rproc_timer *timers = oproc->timers;
+	struct omap_rproc_timer *wd_timer = NULL;
+	int num_timers = oproc->num_timers + oproc->num_wd_timers;
+	int i;
+
+	for (i = oproc->num_timers; i < num_timers; i++) {
+		if (timers[i].irq > 0 && irq == timers[i].irq) {
+			wd_timer = &timers[i];
+			break;
+		}
+	}
+
+	if (!wd_timer) {
+		dev_err(dev, "invalid timer\n");
+		return IRQ_NONE;
+	}
+
+	omap_rproc_ack_timer_irq(wd_timer);
+
+	rproc_report_crash(rproc, RPROC_WATCHDOG);
+
+	return IRQ_HANDLED;
+}
+
 /**
  * omap_rproc_enable_timers() - enable the timers for a remoteproc
  * @rproc: handle of a remote processor
@@ -242,19 +320,26 @@ static int omap_rproc_enable_timers(struct rproc *rproc, bool configure)
 	struct omap_rproc_timer *timers = oproc->timers;
 	struct device *dev = rproc->dev.parent;
 	struct device_node *np = NULL;
+	int num_timers = oproc->num_timers + oproc->num_wd_timers;
 
-	if (!oproc->num_timers)
+	if (!num_timers)
 		return 0;
 
 	if (!configure)
 		goto start_timers;
 
-	for (i = 0; i < oproc->num_timers; i++) {
-		np = of_parse_phandle(dev->of_node, "ti,timers", i);
+	for (i = 0; i < num_timers; i++) {
+		if (i < oproc->num_timers)
+			np = of_parse_phandle(dev->of_node, "ti,timers", i);
+		else
+			np = of_parse_phandle(dev->of_node,
+					      "ti,watchdog-timers",
+					      (i - oproc->num_timers));
 		if (!np) {
 			ret = -ENXIO;
 			dev_err(dev, "device node lookup for timer at index %d failed: %d\n",
-				i, ret);
+				i < oproc->num_timers ? i :
+				i - oproc->num_timers, ret);
 			goto free_timers;
 		}
 
@@ -277,12 +362,14 @@ static int omap_rproc_enable_timers(struct rproc *rproc, bool configure)
 		if (!timer_ops || !timer_ops->request_by_node ||
 		    !timer_ops->set_source || !timer_ops->set_load ||
 		    !timer_ops->free || !timer_ops->start ||
-		    !timer_ops->stop) {
+		    !timer_ops->stop || !timer_ops->get_irq ||
+		    !timer_ops->write_status) {
 			ret = -EINVAL;
 			dev_err(dev, "device does not have required timer ops\n");
 			goto put_node;
 		}
 
+		timers[i].irq = -1;
 		timers[i].timer_ops = timer_ops;
 		ret = omap_rproc_request_timer(dev, np, &timers[i]);
 		if (ret) {
@@ -291,10 +378,33 @@ static int omap_rproc_enable_timers(struct rproc *rproc, bool configure)
 			goto put_node;
 		}
 		of_node_put(np);
+
+		if (i >= oproc->num_timers) {
+			timers[i].irq = omap_rproc_get_timer_irq(&timers[i]);
+			if (timers[i].irq < 0) {
+				dev_err(dev, "get_irq for timer %p failed: %d\n",
+					np, timers[i].irq);
+				ret = -EBUSY;
+				goto free_timers;
+			}
+
+			ret = request_irq(timers[i].irq,
+					  omap_rproc_watchdog_isr, IRQF_SHARED,
+					  "rproc-wdt", rproc);
+			if (ret) {
+				dev_err(dev, "error requesting irq for timer %p\n",
+					np);
+				omap_rproc_release_timer(&timers[i]);
+				timers[i].odt = NULL;
+				timers[i].timer_ops = NULL;
+				timers[i].irq = -1;
+				goto free_timers;
+			}
+		}
 	}
 
 start_timers:
-	for (i = 0; i < oproc->num_timers; i++) {
+	for (i = 0; i < num_timers; i++) {
 		ret = omap_rproc_start_timer(&timers[i]);
 		if (ret) {
 			dev_err(dev, "start timer %p failed failed: %d\n", np,
@@ -316,9 +426,12 @@ static int omap_rproc_enable_timers(struct rproc *rproc, bool configure)
 		of_node_put(np);
 free_timers:
 	while (i--) {
+		if (i >= oproc->num_timers)
+			free_irq(timers[i].irq, rproc);
 		omap_rproc_release_timer(&timers[i]);
 		timers[i].odt = NULL;
 		timers[i].timer_ops = NULL;
+		timers[i].irq = -1;
 	}
 
 	return ret;
@@ -341,16 +454,20 @@ static int omap_rproc_disable_timers(struct rproc *rproc, bool configure)
 	int i;
 	struct omap_rproc *oproc = rproc->priv;
 	struct omap_rproc_timer *timers = oproc->timers;
+	int num_timers = oproc->num_timers + oproc->num_wd_timers;
 
-	if (!oproc->num_timers)
+	if (!num_timers)
 		return 0;
 
-	for (i = 0; i < oproc->num_timers; i++) {
+	for (i = 0; i < num_timers; i++) {
 		omap_rproc_stop_timer(&timers[i]);
 		if (configure) {
+			if (i >= oproc->num_timers)
+				free_irq(timers[i].irq, rproc);
 			omap_rproc_release_timer(&timers[i]);
 			timers[i].odt = NULL;
 			timers[i].timer_ops = NULL;
+			timers[i].irq = -1;
 		}
 	}
 
@@ -1104,12 +1221,35 @@ static int omap_rproc_of_get_internal_memories(struct platform_device *pdev,
 	return 0;
 }
 
+#ifdef CONFIG_OMAP_REMOTEPROC_WATCHDOG
+static int omap_rproc_count_wdog_timers(struct device *dev)
+{
+	struct device_node *np = dev->of_node;
+	int ret;
+
+	ret = of_count_phandle_with_args(np, "ti,watchdog-timers", NULL);
+	if (ret <= 0) {
+		dev_dbg(dev, "device does not have watchdog timers, status = %d\n",
+			ret);
+		ret = 0;
+	}
+
+	return ret;
+}
+#else
+static int omap_rproc_count_wdog_timers(struct device *dev)
+{
+	return 0;
+}
+#endif
+
 static int omap_rproc_of_get_timers(struct platform_device *pdev,
 				    struct rproc *rproc)
 {
 	struct device_node *np = pdev->dev.of_node;
 	struct omap_rproc *oproc = rproc->priv;
 	struct device *dev = &pdev->dev;
+	int num_timers;
 
 	/*
 	 * Timer nodes are directly used in client nodes as phandles, so
@@ -1122,14 +1262,18 @@ static int omap_rproc_of_get_timers(struct platform_device *pdev,
 		oproc->num_timers = 0;
 	}
 
-	if (oproc->num_timers) {
-		oproc->timers = devm_kcalloc(dev, oproc->num_timers,
+	oproc->num_wd_timers = omap_rproc_count_wdog_timers(dev);
+
+	num_timers = oproc->num_timers + oproc->num_wd_timers;
+	if (num_timers) {
+		oproc->timers = devm_kcalloc(dev, num_timers,
 					     sizeof(*oproc->timers),
 					     GFP_KERNEL);
 		if (!oproc->timers)
 			return -ENOMEM;
 
-		dev_dbg(dev, "device has %d tick timers\n", oproc->num_timers);
+		dev_dbg(dev, "device has %d tick timers and %d watchdog timers\n",
+			oproc->num_timers, oproc->num_wd_timers);
 	}
 
 	return 0;