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

Rishabh Bhatnagar
2020-08-27T19:49:40Z

Expose recovery 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@codeaurora.org>
---
Documentation/ABI/testing/sysfs-class-remoteproc | 20 ++++++++
drivers/remoteproc/remoteproc_debugfs.c | 6 ++-
drivers/remoteproc/remoteproc_sysfs.c | 58 ++++++++++++++++++++++++
3 files changed, 82 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-remoteproc b/Documentation/ABI/testing/sysfs-class-remoteproc
index f6c44fa..7368b50 100644
--- a/Documentation/ABI/testing/sysfs-class-remoteproc
+++ b/Documentation/ABI/testing/sysfs-class-remoteproc
@@ -82,3 +82,23 @@ Description: Remote processor coredump configuration
all data is read by usersapce.

"disabled" means no dump will be collected.
+
+What: /sys/class/remoteproc/.../recovery
+Date: July 2020
+Contact: Bjorn Andersson <bjorn.andersson@linaro.org>, Ohad Ben-Cohen <ohad@wizery.com>
+Description: Remote processor recovery mechanism
+
+ Reports the recovery mechanism of the remote processor,
+ which will be one of:
+
+ "enabled"
+ "disabled"
+
+ "enabled" means, the remote processor will be automatically
+ recovered whenever it crashes. Moreover, if the remote
+ processor crashes while recovery is disabled, it will
+ be automatically recovered too as soon as recovery is enabled.
+
+ "disabled" means, a remote processor will remain in a crashed
+ state if it crashes. This is useful for debugging purposes;
+ without it, debugging a crash is substantially harder.
diff --git a/drivers/remoteproc/remoteproc_debugfs.c b/drivers/remoteproc/remoteproc_debugfs.c
index 48dfd0a..415a9ff 100644
--- a/drivers/remoteproc/remoteproc_debugfs.c
+++ b/drivers/remoteproc/remoteproc_debugfs.c
@@ -174,6 +174,7 @@ static const struct file_operations rproc_name_ops = {
.llseek = generic_file_llseek,
};

+#if (!IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT))
/* expose recovery flag via debugfs */
static ssize_t rproc_recovery_read(struct file *filp, char __user *userbuf,
size_t count, loff_t *ppos)
@@ -249,6 +250,7 @@ static const struct file_operations rproc_recovery_ops = {
.open = simple_open,
.llseek = generic_file_llseek,
};
+#endif

/* expose the crash trigger via debugfs */
static ssize_t
@@ -419,8 +421,6 @@ void rproc_create_debug_dir(struct rproc *rproc)

debugfs_create_file("name", 0400, rproc->dbg_dir,
rproc, &rproc_name_ops);
- debugfs_create_file("recovery", 0600, rproc->dbg_dir,
- rproc, &rproc_recovery_ops);
debugfs_create_file("crash", 0200, rproc->dbg_dir,
rproc, &rproc_crash_ops);
debugfs_create_file("resource_table", 0400, rproc->dbg_dir,
@@ -430,6 +430,8 @@ void rproc_create_debug_dir(struct rproc *rproc)
#if (!IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT))
debugfs_create_file("coredump", 0600, rproc->dbg_dir,
rproc, &rproc_coredump_fops);
+ debugfs_create_file("recovery", 0600, rproc->dbg_dir,
+ rproc, &rproc_recovery_ops);
#endif
}

diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
index 89b301a..45cae4f 100644
--- a/drivers/remoteproc/remoteproc_sysfs.c
+++ b/drivers/remoteproc/remoteproc_sysfs.c
@@ -11,6 +11,63 @@
#define to_rproc(d) container_of(d, struct rproc, dev)

#if IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT)
+
+/* expose recovery flag via sysfs */
+static ssize_t recovery_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct rproc *rproc = to_rproc(dev);
+
+ return sprintf(buf, "%s", rproc->recovery_disabled ? "disabled\n" : "enabled\n");
+}
+
+/*
+ * By writing to the 'recovery' sysfs entry, we control the behavior of the
+ * recovery mechanism dynamically. The default value of this entry is "enabled".
+ *
+ * The 'recovery' sysfs entry supports these commands:
+ *
+ * enabled: When enabled, the remote processor will be automatically
+ * recovered whenever it crashes. Moreover, if the remote
+ * processor crashes while recovery is disabled, it will
+ * be automatically recovered too as soon as recovery is enabled.
+ *
+ * disabled: When disabled, a remote processor will remain in a crashed
+ * state if it crashes. This is useful for debugging purposes;
+ * without it, debugging a crash is substantially harder.
+ *
+ * recover: This function will trigger an immediate recovery if the
+ * remote processor is in a crashed state, without changing
+ * or checking the recovery state (enabled/disabled).
+ * This is useful during debugging sessions, when one expects
+ * additional crashes to happen after enabling recovery. In this
+ * case, enabling recovery will make it hard to debug subsequent
+ * crashes, so it's recommended to keep recovery disabled, and
+ * instead use the "recover" command as needed.
+ */
+static ssize_t recovery_store(struct device *dev,
+ struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct rproc *rproc = to_rproc(dev);
+
+ if (sysfs_streq(buf, "enabled")) {
+ /* change the flag and begin the recovery process if needed */
+ rproc->recovery_disabled = false;
+ rproc_trigger_recovery(rproc);
+ } else if (sysfs_streq(buf, "disabled")) {
+ rproc->recovery_disabled = true;
+ } else if (sysfs_streq(buf, "recover")) {
+ /* begin the recovery process without changing the flag */
+ rproc_trigger_recovery(rproc);
+ } else {
+ return -EINVAL;
+ }
+
+ return count;
+}
+static DEVICE_ATTR_RW(recovery);
+
/*
* A coredump-configuration-to-string lookup table, for exposing a
* human readable configuration via sysfs. Always keep in sync with
@@ -205,6 +262,7 @@ static DEVICE_ATTR_RO(name);
static struct attribute *rproc_attrs[] = {
#if IS_ENABLED(CONFIG_RPROC_SYSFS_CONFIGURATION_SUPPORT)
&dev_attr_coredump.attr,
+ &dev_attr_recovery.attr,
#endif
&dev_attr_firmware.attr,
&dev_attr_state.attr,
--
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