[PATCH v2 1/5] remoteproc: Add support for detach-only during shutdown

[Suman Anna <s-anna@ti.com>]

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.

Enhance the remoteproc core logic to key off the presence of the
.stop() ops and allow the individual remoteproc drivers to continue
to use the standard rproc_add() and rproc_del() API. This allows
the remoteproc drivers to only do detach if supported when the driver
is uninstalled, and the remote processor continues to run undisturbed
even after the driver removal.

Signed-off-by: Suman Anna <s-anna@ti.com>
---
v2: Addressed various review comments from v1
 - Reworked the logic to not use remoteproc detach_on_shutdown and
   rely only on rproc callback ops
 - Updated the last para of the patch description
v1: https://patchwork.kernel.org/project/linux-remoteproc/patch/20210522000309.26134-3-s-anna@ti.com/

 drivers/remoteproc/remoteproc_cdev.c  | 7 +++++++
 drivers/remoteproc/remoteproc_core.c  | 5 ++++-
 drivers/remoteproc/remoteproc_sysfs.c | 6 ++++++
 3 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_cdev.c b/drivers/remoteproc/remoteproc_cdev.c
index 4ad98b0b8caa..16c932beed88 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->ops->stop) {
+			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 7de5905d276a..ab9e52180b04 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -2075,7 +2075,10 @@ void rproc_shutdown(struct rproc *rproc)
 	if (!atomic_dec_and_test(&rproc->power))
 		goto out;
 
-	ret = rproc_stop(rproc, false);
+	if (rproc->state == RPROC_ATTACHED && !rproc->ops->stop)
+		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..133e766f38d4 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->ops->stop) {
+			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)
-- 
2.32.0