remoteproc: Add a sysfs interface for firmware and state

This patch adds a sysfs interface to rproc allowing the firmware name
and processor state to be changed dynamically.

State was previously available in debugfs, and is replicated here. The
firmware file allows retrieval of the running firmware name, and a new
one to be specified at run time, so long as the remote processor has
been stopped.
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

Documentation/ABI/testing/sysfs-class-remoteproc

+What:		/sys/class/remoteproc/.../firmware
+Date:		October 2016
+Contact:	Matt Redfearn <matt.redfearn@imgtec.com>
+Description:	Remote processor firmware
+
+		Reports the name of the firmware currently loaded to the
+		remote processor.
+
+		To change the running firmware, ensure the remote processor is
+		stopped (using /sys/class/remoteproc/.../state) and write a new filename.
+
+What:		/sys/class/remoteproc/.../state
+Date:		October 2016
+Contact:	Matt Redfearn <matt.redfearn@imgtec.com>
+Description:	Remote processor state
+
+		Reports the state of the remote processor, which will be one of:
+
+		"offline"
+		"suspended"
+		"running"
+		"crashed"
+		"invalid"
+
+		"offline" means the remote processor is powered off.
+
+		"suspended" means that the remote processor is suspended and
+		must be woken to receive messages.
+
+		"running" is the normal state of an available remote processor
+
+		"crashed" indicates that a problem/crash has been detected on
+		the remote processor.
+
+		"invalid" is returned if the remote processor is in an
+		unknown state.
+
+		Writing this file controls the state of the remote processor.
+		The following states can be written:
+
+		"start"
+		"stop"
+
+		Writing "start" will attempt to start the processor running the
+		firmware indicated by, or written to,
+		/sys/class/remoteproc/.../firmware. The remote processor should
+		transition to "running" state.
+
+		Writing "stop" will attempt to halt the remote processor and
+		return it to the "offline" state.

drivers/remoteproc/Makefile

@@ -5,6 +5,7 @@
 obj-$(CONFIG_REMOTEPROC)		+= remoteproc.o
 remoteproc-y				:= remoteproc_core.o
 remoteproc-y				+= remoteproc_debugfs.o
+remoteproc-y				+= remoteproc_sysfs.o
 remoteproc-y				+= remoteproc_virtio.o
 remoteproc-y				+= remoteproc_elf_loader.o
 obj-$(CONFIG_OMAP_REMOTEPROC)		+= omap_remoteproc.o

drivers/remoteproc/remoteproc_core.c

@@ -1347,6 +1347,7 @@ struct rproc *rproc_alloc(struct device *dev, const char *name,
 	device_initialize(&rproc->dev);
 	rproc->dev.parent = dev;
 	rproc->dev.type = &rproc_type;
+	rproc->dev.class = &rproc_class;
 
 	/* Assign a unique device index and name */
 	rproc->index = ida_simple_get(&rproc_dev_index, 0, 0, GFP_KERNEL);
@@ -1485,6 +1486,7 @@ EXPORT_SYMBOL(rproc_report_crash);
 
 static int __init remoteproc_init(void)
 {
+	rproc_init_sysfs();
 	rproc_init_debugfs();
 
 	return 0;
@@ -1496,6 +1498,7 @@ static void __exit remoteproc_exit(void)
 	ida_destroy(&rproc_dev_index);
 
 	rproc_exit_debugfs();
+	rproc_exit_sysfs();
 }
 module_exit(remoteproc_exit);
 

drivers/remoteproc/remoteproc_internal.h

@@ -63,6 +63,11 @@ void rproc_create_debug_dir(struct rproc *rproc);
 void rproc_init_debugfs(void);
 void rproc_exit_debugfs(void);
 
+/* from remoteproc_sysfs.c */
+extern struct class rproc_class;
+int rproc_init_sysfs(void);
+void rproc_exit_sysfs(void);
+
 void rproc_free_vring(struct rproc_vring *rvring);
 int rproc_alloc_vring(struct rproc_vdev *rvdev, int i);
 

drivers/remoteproc/remoteproc_sysfs.c

+/*
+ * Remote Processor Framework
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/remoteproc.h>
+
+#include "remoteproc_internal.h"
+
+#define to_rproc(d) container_of(d, struct rproc, dev)
+
+/* Expose the loaded / running firmware name via sysfs */
+static ssize_t firmware_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct rproc *rproc = to_rproc(dev);
+
+	return sprintf(buf, "%s\n", rproc->firmware);
+}
+
+/* Change firmware name via sysfs */
+static ssize_t firmware_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct rproc *rproc = to_rproc(dev);
+	char *p;
+	int err, len = count;
+
+	err = mutex_lock_interruptible(&rproc->lock);
+	if (err) {
+		dev_err(dev, "can't lock rproc %s: %d\n", rproc->name, err);
+		return -EINVAL;
+	}
+
+	if (rproc->state != RPROC_OFFLINE) {
+		dev_err(dev, "can't change firmware while running\n");
+		err = -EBUSY;
+		goto out;
+	}
+
+	len = strcspn(buf, "\n");
+
+	p = kstrndup(buf, len, GFP_KERNEL);
+	if (!p) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	kfree(rproc->firmware);
+	rproc->firmware = p;
+out:
+	mutex_unlock(&rproc->lock);
+
+	return err ? err : count;
+}
+static DEVICE_ATTR_RW(firmware);
+
+/*
+ * A state-to-string lookup table, for exposing a human readable state
+ * via sysfs. Always keep in sync with enum rproc_state
+ */
+static const char * const rproc_state_string[] = {
+	[RPROC_OFFLINE]		= "offline",
+	[RPROC_SUSPENDED]	= "suspended",
+	[RPROC_RUNNING]		= "running",
+	[RPROC_CRASHED]		= "crashed",
+	[RPROC_LAST]		= "invalid",
+};
+
+/* Expose the state of the remote processor via sysfs */
+static ssize_t state_show(struct device *dev, struct device_attribute *attr,
+			  char *buf)
+{
+	struct rproc *rproc = to_rproc(dev);
+	unsigned int state;
+
+	state = rproc->state > RPROC_LAST ? RPROC_LAST : rproc->state;
+	return sprintf(buf, "%s\n", rproc_state_string[state]);
+}
+
+/* Change remote processor state via sysfs */
+static ssize_t state_store(struct device *dev,
+			      struct device_attribute *attr,
+			      const char *buf, size_t count)
+{
+	struct rproc *rproc = to_rproc(dev);
+	int ret = 0;
+
+	if (sysfs_streq(buf, "start")) {
+		if (rproc->state == RPROC_RUNNING)
+			return -EBUSY;
+
+		ret = rproc_boot(rproc);
+		if (ret)
+			dev_err(&rproc->dev, "Boot failed: %d\n", ret);
+	} else if (sysfs_streq(buf, "stop")) {
+		if (rproc->state != RPROC_RUNNING)
+			return -EINVAL;
+
+		rproc_shutdown(rproc);
+	} else {
+		dev_err(&rproc->dev, "Unrecognised option: %s\n", buf);
+		ret = -EINVAL;
+	}
+	return ret ? ret : count;
+}
+static DEVICE_ATTR_RW(state);
+
+static struct attribute *rproc_attrs[] = {
+	&dev_attr_firmware.attr,
+	&dev_attr_state.attr,
+	NULL
+};
+
+static const struct attribute_group rproc_devgroup = {
+	.attrs = rproc_attrs
+};
+
+static const struct attribute_group *rproc_devgroups[] = {
+	&rproc_devgroup,
+	NULL
+};
+
+struct class rproc_class = {
+	.name		= "remoteproc",
+	.dev_groups	= rproc_devgroups,
+};
+
+int __init rproc_init_sysfs(void)
+{
+	/* create remoteproc device class for sysfs */
+	int err = class_register(&rproc_class);
+
+	if (err)
+		pr_err("remoteproc: unable to register class\n");
+	return err;
+}
+
+void __exit rproc_exit_sysfs(void)
+{
+	class_unregister(&rproc_class);
+}