remoteproc: Properly deal with a stop request when attached

Allow a remote processor that was started by another entity to be
switched off by the remoteproc core. For that to happen a
rproc::ops::stop() operation needs to be available.

Signed-off-by: Mathieu Poirier <[e-mail]>
Reviewed-by: Arnaud Pouliquen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Bjorn Andersson <[e-mail]>

drivers/remoteproc/remoteproc_cdev.c

···
 
 		ret = rproc_boot(rproc);
 	} else if (!strncmp(cmd, "stop", len)) {
-		if (rproc->state != RPROC_RUNNING)
+		if (rproc->state != RPROC_RUNNING &&
+		    rproc->state != RPROC_ATTACHED)
 			return -EINVAL;
 
 		rproc_shutdown(rproc);

drivers/remoteproc/remoteproc_core.c

···
 	struct device *dev = &rproc->dev;
 	int ret;
 
+	/* No need to continue if a stop() operation has not been provided */
+	if (!rproc->ops->stop)
+		return -EINVAL;
+
 	/* Stop any subdevices for the remote processor */
 	rproc_stop_subdevices(rproc, crashed);
 

drivers/remoteproc/remoteproc_sysfs.c

···
 		if (ret)
 			dev_err(&rproc->dev, "Boot failed: %d\n", ret);
 	} else if (sysfs_streq(buf, "stop")) {
-		if (rproc->state != RPROC_RUNNING)
+		if (rproc->state != RPROC_RUNNING &&
+		    rproc->state != RPROC_ATTACHED)
 			return -EINVAL;
 
 		rproc_shutdown(rproc);