remoteproc: Introduce "panic" callback in ops

Introduce generic support for handling kernel panics in remoteproc
drivers, in order to allow operations needed for aiding in post mortem
system debugging, such as flushing caches etc.

The function can return a number of milliseconds needed by the remote to
"settle" and the core will wait the longest returned duration before
returning from the panic handler.

Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200324052904.738594-3-bjorn.andersson@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index 7ee976ee2044..e12a54e67588 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -16,6 +16,7 @@
 
 #define pr_fmt(fmt)    "%s: " fmt, __func__
 
+#include <linux/delay.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/device.h>
@@ -45,6 +46,7 @@
 
 static DEFINE_MUTEX(rproc_list_mutex);
 static LIST_HEAD(rproc_list);
+static struct notifier_block rproc_panic_nb;
 
 typedef int (*rproc_handle_resource_t)(struct rproc *rproc,
 				 void *, int offset, int avail);
@@ -2236,10 +2238,50 @@ void rproc_report_crash(struct rproc *rproc, enum rproc_crash_type type)
 }
 EXPORT_SYMBOL(rproc_report_crash);
 
+static int rproc_panic_handler(struct notifier_block *nb, unsigned long event,
+			       void *ptr)
+{
+	unsigned int longest = 0;
+	struct rproc *rproc;
+	unsigned int d;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(rproc, &rproc_list, node) {
+		if (!rproc->ops->panic || rproc->state != RPROC_RUNNING)
+			continue;
+
+		d = rproc->ops->panic(rproc);
+		longest = max(longest, d);
+	}
+	rcu_read_unlock();
+
+	/*
+	 * Delay for the longest requested duration before returning. This can
+	 * be used by the remoteproc drivers to give the remote processor time
+	 * to perform any requested operations (such as flush caches), when
+	 * it's not possible to signal the Linux side due to the panic.
+	 */
+	mdelay(longest);
+
+	return NOTIFY_DONE;
+}
+
+static void __init rproc_init_panic(void)
+{
+	rproc_panic_nb.notifier_call = rproc_panic_handler;
+	atomic_notifier_chain_register(&panic_notifier_list, &rproc_panic_nb);
+}
+
+static void __exit rproc_exit_panic(void)
+{
+	atomic_notifier_chain_unregister(&panic_notifier_list, &rproc_panic_nb);
+}
+
 static int __init remoteproc_init(void)
 {
 	rproc_init_sysfs();
 	rproc_init_debugfs();
+	rproc_init_panic();
 
 	return 0;
 }
@@ -2249,6 +2291,7 @@ static void __exit remoteproc_exit(void)
 {
 	ida_destroy(&rproc_dev_index);
 
+	rproc_exit_panic();
 	rproc_exit_debugfs();
 	rproc_exit_sysfs();
 }