remoteproc: Properly deal with a detach request when attached

This patch introduces the capability to detach a remote processor
that has been attached to by the remoteproc core.  For that to happen
a rproc::ops::detach() operation needs to be available.
Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Arnaud Pouliquen <arnaud.pouliquen@st.com>
Link: https://lore.kernel.org/r/20210312162453.1234145-17-mathieu.poirier@linaro.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_cdev.c

@@ -43,6 +43,11 @@ static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_
 			return -EINVAL;
 
 		rproc_shutdown(rproc);
+	} else if (!strncmp(cmd, "detach", len)) {
+		if (rproc->state != RPROC_ATTACHED)
+			return -EINVAL;
+
+		ret = rproc_detach(rproc);
 	} else {
 		dev_err(&rproc->dev, "Unrecognized option\n");
 		ret = -EINVAL;

drivers/remoteproc/remoteproc_sysfs.c

@@ -207,6 +207,11 @@ static ssize_t state_store(struct device *dev,
 			return -EINVAL;
 
 		rproc_shutdown(rproc);
+	} else if (sysfs_streq(buf, "detach")) {
+		if (rproc->state != RPROC_ATTACHED)
+			return -EINVAL;
+
+		ret = rproc_detach(rproc);
 	} else {
 		dev_err(&rproc->dev, "Unrecognised option: %s\n", buf);
 		ret = -EINVAL;