[PATCH v2 2/3] remoteproc: Add coredump configuration to sysfs

[Rishabh Bhatnagar]

Expose coredump configuration in sysfs under a feature
flag. This is useful for systems where access to
debugfs might be limited.

Signed-off-by: Rishabh Bhatnagar <rishabhb@xxxxxxxxxxxxxx>
---
 Documentation/ABI/testing/sysfs-class-remoteproc | 24 +++++++++
 drivers/remoteproc/remoteproc_debugfs.c          |  4 ++
 drivers/remoteproc/remoteproc_sysfs.c            | 68 ++++++++++++++++++++++++
 3 files changed, 96 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-class-remoteproc b/Documentation/ABI/testing/sysfs-class-remoteproc
index 36094fb..f6c44fa 100644
--- a/Documentation/ABI/testing/sysfs-class-remoteproc
+++ b/Documentation/ABI/testing/sysfs-class-remoteproc
@@ -58,3 +58,27 @@ Description:	Remote processor name
 		Reports the name of the remote processor. This can be used by
 		userspace in exactly identifying a remote processor and ease
 		up the usage in modifying the 'firmware' or 'state' files.
+
+What:		/sys/class/remoteproc/.../coredump
+Date:		July 2020
+Contact:	Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>, Ohad Ben-Cohen <ohad@xxxxxxxxxx>
+Description:	Remote processor coredump configuration
+
+		Reports the coredump configuration of the remote processor,
+		which will be one of:
+
+		"default"
+		"inline"
+		"disabled"
+
+		"default" means when the remote processor's coredump is
+		collected it will be copied to a separate buffer and that
+		buffer is exposed to userspace.
+
+		"inline" means when the remote processor's coredump is
+		collected userspace will directly read from the remote
+		processor's device memory. Extra buffer will not be used to
+		copy the dump. Also recovery process will not proceed until
+		all data is read by usersapce.
+
+		"disabled" means no dump will be collected.
diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
index 2e3b3e2..48dfd0a 100644
--- a/drivers/remoteproc/remoteproc_debugfs.c
+++ b/drivers/remoteproc/remoteproc_debugfs.c
@@ -27,6 +27,7 @@
 /* remoteproc debugfs parent dir */
 static struct dentry *rproc_dbg;
 
+#if (!IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT))
 /*
  * A coredump-configuration-to-string lookup table, for exposing a
  * human readable configuration via debugfs. Always keep in sync with
@@ -114,6 +115,7 @@ static const struct file_operations rproc_coredump_fops = {
 	.open = simple_open,
 	.llseek = generic_file_llseek,
 };
+#endif
 
 /*
  * Some remote processors may support dumping trace logs into a shared
@@ -425,8 +427,10 @@ void rproc_create_debug_dir(struct rproc *rproc)
 			    rproc, &rproc_rsc_table_fops);
 	debugfs_create_file("carveout_memories", 0400, rproc->dbg_dir,
 			    rproc, &rproc_carveouts_fops);
+#if (!IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT))
 	debugfs_create_file("coredump", 0600, rproc->dbg_dir,
 			    rproc, &rproc_coredump_fops);
+#endif
 }
 
 void __init rproc_init_debugfs(void)
diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
index eea514c..89b301a 100644
--- a/drivers/remoteproc/remoteproc_sysfs.c
+++ b/drivers/remoteproc/remoteproc_sysfs.c
@@ -10,6 +10,71 @@
 
 #define to_rproc(d) container_of(d, struct rproc, dev)
 
+#if IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT)
+/*
+ * A coredump-configuration-to-string lookup table, for exposing a
+ * human readable configuration via sysfs. Always keep in sync with
+ * enum rproc_coredump_mechanism
+ */
+static const char * const rproc_coredump_str[] = {
+	[RPROC_COREDUMP_DEFAULT]	= "default",
+	[RPROC_COREDUMP_INLINE]		= "inline",
+	[RPROC_COREDUMP_DISABLED]	= "disabled",
+};
+
+/* Expose the current coredump configuration via debugfs */
+static ssize_t coredump_show(struct device *dev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct rproc *rproc = to_rproc(dev);
+
+	return sprintf(buf, "%s\n", rproc_coredump_str[rproc->dump_conf]);
+}
+
+/*
+ * By writing to the 'coredump' sysfs entry, we control the behavior of the
+ * coredump mechanism dynamically. The default value of this entry is "default".
+ *
+ * The 'coredump' sysfs entry supports these commands:
+ *
+ * default:	This is the default coredump mechanism. When the remoteproc
+ *		crashes the entire coredump will be copied to a separate buffer
+ *		and exposed to userspace.
+ *
+ * inline:	The coredump will not be copied to a separate buffer and the
+ *		recovery process will have to wait until data is read by
+ *		userspace. But this avoid usage of extra memory.
+ *
+ * disabled:	This will disable coredump. Recovery will proceed without
+ *		collecting any dump.
+ */
+static ssize_t coredump_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct rproc *rproc = to_rproc(dev);
+
+	if (rproc->state == RPROC_CRASHED) {
+		dev_err(&rproc->dev, "can't change coredump configuration\n");
+		return -EBUSY;
+	}
+
+	if (sysfs_streq(buf, "disable")) {
+		rproc->dump_conf = RPROC_COREDUMP_DISABLED;
+	} else if (sysfs_streq(buf, "inline")) {
+		rproc->dump_conf = RPROC_COREDUMP_INLINE;
+	} else if (sysfs_streq(buf, "default")) {
+		rproc->dump_conf = RPROC_COREDUMP_DEFAULT;
+	} else {
+		dev_err(&rproc->dev, "Invalid coredump configuration\n");
+		return -EINVAL;
+	}
+
+	return count;
+}
+static DEVICE_ATTR_RW(coredump);
+#endif
+
 /* Expose the loaded / running firmware name via sysfs */
 static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
@@ -138,6 +203,9 @@ static ssize_t name_show(struct device *dev, struct device_attribute *attr,
 static DEVICE_ATTR_RO(name);
 
 static struct attribute *rproc_attrs[] = {
+#if IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT)
+	&dev_attr_coredump.attr,
+#endif
 	&dev_attr_firmware.attr,
 	&dev_attr_state.attr,
 	&dev_attr_name.attr,
-- 
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