remoteproc: core: Remove state checking before calling rproc_boot()

There is no mutex protection of the state checking before rproc_boot(),
which can't guarantee there is no another instance is trying to do
same operation.

Consider two instances case:
Instance1: echo start > /sys/class/remoteproc/remoteproc0/state
Instance2: echo start > /sys/class/remoteproc/remoteproc0/state
...
Instance2: echo stop > /sys/class/remoteproc/remoteproc0/state
...
Instance1: echo stop > /sys/class/remoteproc/remoteproc0/state

The one issue is that the instance2 case may success when 'start'
happens at same time as instance1, then rproc->power = 2; Or it
may fail with -BUSY, then rproc->power = 1; which is uncertain.

The another issue is for 'stop' operation, if the rproc->power = 1,
when instance2 'stop' the remoteproc the instance1 will be
impacted for it still needs the service at that time.

The reference counter rproc->power is used to manage state
changing and there is mutex protection in each operation
function for multi instance case.

So remove this state checking in rproc_cdev_write() and
state_store() for 'start' operation, just let reference
counter rproc->power to manage the behaviors.

Signed-off-by: Shengjiu Wang <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mathieu Poirier <[email protected]>

Author: TE-N-ShengjiuWang

drivers/remoteproc/remoteproc_cdev.c

@@ -32,10 +32,6 @@ static ssize_t rproc_cdev_write(struct file *filp, const char __user *buf, size_
 		return -EFAULT;
 
 	if (!strncmp(cmd, "start", len)) {
-		if (rproc->state == RPROC_RUNNING ||
-		    rproc->state == RPROC_ATTACHED)
-			return -EBUSY;
-
 		ret = rproc_boot(rproc);
 	} else if (!strncmp(cmd, "stop", len)) {
 		if (rproc->state != RPROC_RUNNING &&

drivers/remoteproc/remoteproc_sysfs.c

@@ -194,10 +194,6 @@ static ssize_t state_store(struct device *dev,
 	int ret = 0;
 
 	if (sysfs_streq(buf, "start")) {
-		if (rproc->state == RPROC_RUNNING ||
-		    rproc->state == RPROC_ATTACHED)
-			return -EBUSY;
-
 		ret = rproc_boot(rproc);
 		if (ret)
 			dev_err(&rproc->dev, "Boot failed: %d\n", ret);