[RFC PATCH v3 3/7] coresight: core: Add provision for panic callbacks

[Linu Cherian <lcherian@marvell.com>]

Panic callback handlers allows coresight device drivers to sync
relevant trace data and trace metadata to reserved memory
regions so that they can be retrieved later in the subsequent
boot or in the crashdump kernel.

Signed-off-by: Linu Cherian <lcherian@marvell.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 32 ++++++++++++++++++++
 include/linux/coresight.h                    | 12 ++++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index 118fcf27854d..de4e3947c8e5 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -20,6 +20,7 @@
 #include <linux/of_platform.h>
 #include <linux/delay.h>
 #include <linux/pm_runtime.h>
+#include <linux/panic_notifier.h>
 
 #include "coresight-etm-perf.h"
 #include "coresight-priv.h"
@@ -1800,6 +1801,31 @@ struct bus_type coresight_bustype = {
 	.name	= "coresight",
 };
 
+static int coresight_panic_sync(struct device *dev, void *data)
+{
+
+	struct coresight_device *csdev = container_of(dev, struct coresight_device, dev);
+
+	/* Run through panic sync handlers for all enabled devices */
+	if (csdev->enable && panic_ops(csdev))
+		panic_ops(csdev)->sync(csdev);
+
+	return 0;
+}
+
+static int coresight_panic_cb(struct notifier_block *self,
+			       unsigned long v, void *p)
+{
+	bus_for_each_dev(&coresight_bustype, NULL, NULL,
+				 coresight_panic_sync);
+
+	return 0;
+}
+
+static struct notifier_block coresight_notifier = {
+	.notifier_call = coresight_panic_cb,
+};
+
 static int __init coresight_init(void)
 {
 	int ret;
@@ -1812,6 +1838,10 @@ static int __init coresight_init(void)
 	if (ret)
 		goto exit_bus_unregister;
 
+	/* Register function to be called for panic */
+	ret = atomic_notifier_chain_register(&panic_notifier_list,
+					     &coresight_notifier);
+
 	/* initialise the coresight syscfg API */
 	ret = cscfg_init();
 	if (!ret)
@@ -1826,6 +1856,8 @@ static int __init coresight_init(void)
 static void __exit coresight_exit(void)
 {
 	cscfg_exit();
+	atomic_notifier_chain_unregister(&panic_notifier_list,
+					     &coresight_notifier);
 	etm_perf_exit();
 	bus_unregister(&coresight_bustype);
 }
diff --git a/include/linux/coresight.h b/include/linux/coresight.h
index bf70987240e4..09978ea6abe1 100644
--- a/include/linux/coresight.h
+++ b/include/linux/coresight.h
@@ -299,6 +299,7 @@ enum cs_mode {
 #define link_ops(csdev)		csdev->ops->link_ops
 #define helper_ops(csdev)	csdev->ops->helper_ops
 #define ect_ops(csdev)		csdev->ops->ect_ops
+#define panic_ops(csdev)	csdev->ops->panic_ops
 
 /**
  * struct coresight_ops_sink - basic operations for a sink
@@ -368,11 +369,22 @@ struct coresight_ops_helper {
 	int (*disable)(struct coresight_device *csdev, void *data);
 };
 
+
+/**
+ * struct coresight_ops_panic - Generic device ops for panic handing
+ *
+ * @sync	: Sync the device register state/trace data
+ */
+struct coresight_ops_panic {
+	int (*sync)(struct coresight_device *csdev);
+};
+
 struct coresight_ops {
 	const struct coresight_ops_sink *sink_ops;
 	const struct coresight_ops_link *link_ops;
 	const struct coresight_ops_source *source_ops;
 	const struct coresight_ops_helper *helper_ops;
+	const struct coresight_ops_panic *panic_ops;
 };
 
 #if IS_ENABLED(CONFIG_CORESIGHT)
-- 
2.41.0