[PATCH 2/6] remoteproc: Add support for detach-only during shutdown

[Suman Anna]

The remoteproc core has support for both stopping and detaching a
remote processor that was attached to previously, through both the
remoteproc sysfs and cdev interfaces. The rproc_shutdown() though
unconditionally only uses the stop functionality at present. This
may not be the default desired functionality for all the remoteproc
platform drivers.

Introduce a new rproc state flag 'detach_on_shutdown' that individual
remoteproc drivers can set to only allow detach in rproc_shutdown()
that would have been invoked when the driver is uninstalled, so that
remote processor continues to run undisturbed even after the driver
removal.

Signed-off-by: Suman Anna <s-anna@xxxxxx>
---
 drivers/remoteproc/remoteproc_cdev.c  | 7 +++++++
 drivers/remoteproc/remoteproc_core.c  | 5 ++++-
 drivers/remoteproc/remoteproc_sysfs.c | 6 ++++++
 include/linux/remoteproc.h            | 3 +++
 4 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c
index 0b8a84c04f76..473467711a09 100644
--- a/drivers/remoteproc/remoteproc_cdev.c
+++ b/drivers/remoteproc/remoteproc_cdev.c
@@ -42,6 +42,13 @@ static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_
 		    rproc->state != RPROC_ATTACHED)
 			return -EINVAL;
 
+		if (rproc->state == RPROC_ATTACHED &&
+		    rproc->detach_on_shutdown) {
+			dev_err(&rproc->dev,
+				"stop not supported for this rproc, use detach\n");
+			return -EINVAL;
+		}
+
 		rproc_shutdown(rproc);
 	} else if (!strncmp(cmd, "detach", len)) {
 		if (rproc->state != RPROC_ATTACHED)
diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index 6019f46001c8..e8ab3eb41f00 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -2074,7 +2074,10 @@ void rproc_shutdown(struct rproc *rproc)
 	if (!atomic_dec_and_test(&rproc->power))
 		goto out;
 
-	ret = rproc_stop(rproc, false);
+	if (rproc->detach_on_shutdown && rproc->state == RPROC_ATTACHED)
+		ret = __rproc_detach(rproc);
+	else
+		ret = rproc_stop(rproc, false);
 	if (ret) {
 		atomic_inc(&rproc->power);
 		goto out;
diff --git a/drivers/remoteproc/remoteproc_sysfs.c b/drivers/remoteproc/remoteproc_sysfs.c
index ea8b89f97d7b..1785fbcb1075 100644
--- a/drivers/remoteproc/remoteproc_sysfs.c
+++ b/drivers/remoteproc/remoteproc_sysfs.c
@@ -206,6 +206,12 @@ static ssize_t state_store(struct device *dev,
 		    rproc->state != RPROC_ATTACHED)
 			return -EINVAL;
 
+		if (rproc->state == RPROC_ATTACHED &&
+		    rproc->detach_on_shutdown) {
+			dev_err(&rproc->dev, "stop not supported for this rproc, use detach\n");
+			return -EINVAL;
+		}
+
 		rproc_shutdown(rproc);
 	} else if (sysfs_streq(buf, "detach")) {
 		if (rproc->state != RPROC_ATTACHED)
diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
index 42a1f30e33a7..35ef921676a1 100644
--- a/include/linux/remoteproc.h
+++ b/include/linux/remoteproc.h
@@ -530,6 +530,8 @@ struct rproc_dump_segment {
  * @elf_machine: firmware ELF machine
  * @cdev: character device of the rproc
  * @cdev_put_on_release: flag to indicate if remoteproc should be shutdown on @char_dev release
+ * @detach_on_shutdown: flag to indicate if remoteproc cannot be shutdown in
+ *			attached state and _only_ support detach
  */
 struct rproc {
 	struct list_head node;
@@ -569,6 +571,7 @@ struct rproc {
 	u16 elf_machine;
 	struct cdev cdev;
 	bool cdev_put_on_release;
+	bool detach_on_shutdown;
 };
 
 /**
-- 
2.30.1