remoteproc: maintain a generic child device for each rproc

For each registered rproc, maintain a generic remoteproc device whose
parent is the low level platform-specific device (commonly a pdev, but
it may certainly be any other type of device too).

With this in hand, the resulting device hierarchy might then look like:

omap-rproc.0
 |
 - remoteproc0  <---- new !
    |
    - virtio0
    |
    - virtio1
       |
       - rpmsg0
       |
       - rpmsg1
       |
       - rpmsg2

Where:
- omap-rproc.0 is the low level device that's bound to the
  driver which invokes rproc_register()
- remoteproc0 is the result of this patch, and will be added by the
  remoteproc framework when rproc_register() is invoked
- virtio0 and virtio1 are vdevs that are registered by remoteproc
  when it realizes that they are supported by the firmware
  of the physical remote processor represented by omap-rproc.0
- rpmsg0, rpmsg1 and rpmsg2 are rpmsg devices that represent rpmsg
  channels, and are registerd by the rpmsg bus when it gets notified
  about their existence

Technically, this patch:
- changes 'struct rproc' to contain this generic remoteproc.x device
- creates a new "remoteproc" type, to which this new generic remoteproc.x
  device belong to.
- adds a super simple enumeration method for the indices of the
  remoteproc.x devices
- updates all dev_* messaging to use the generic remoteproc.x device
  instead of the low level platform-specific device
- updates all dma_* allocations to use the parent of remoteproc.x (where
  the platform-specific memory pools, most commonly CMA, are to be found)

Adding this generic device has several merits:
- we can now add remoteproc runtime PM support simply by hooking onto the
  new "remoteproc" type
- all remoteproc log messages will now carry a common name prefix
  instead of having a platform-specific one
- having a device as part of the rproc struct makes it possible to simplify
  refcounting (see subsequent patch)

Thanks to Stephen Boyd <sboyd@codeaurora.org> for suggesting and
discussing these ideas in one of the remoteproc review threads and
to Fernando Guzman Lugo <fernando.lugo@ti.com> for trying them out
with the (upcoming) runtime PM support for remoteproc.

Cc: Fernando Guzman Lugo <fernando.lugo@ti.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>

drivers/remoteproc/remoteproc_virtio.c

@@ -36,7 +36,7 @@ static void rproc_virtio_notify(struct virtqueue *vq)
 	struct rproc *rproc = rvring->rvdev->rproc;
 	int notifyid = rvring->notifyid;
 
-	dev_dbg(rproc->dev, "kicking vq index: %d\n", notifyid);
+	dev_dbg(&rproc->dev, "kicking vq index: %d\n", notifyid);
 
 	rproc->ops->kick(rproc, notifyid);
 }
@@ -57,7 +57,7 @@ irqreturn_t rproc_vq_interrupt(struct rproc *rproc, int notifyid)
 {
 	struct rproc_vring *rvring;
 
-	dev_dbg(rproc->dev, "vq index %d is interrupted\n", notifyid);
+	dev_dbg(&rproc->dev, "vq index %d is interrupted\n", notifyid);
 
 	rvring = idr_find(&rproc->notifyids, notifyid);
 	if (!rvring || !rvring->vq)
@@ -74,6 +74,7 @@ static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
 {
 	struct rproc_vdev *rvdev = vdev_to_rvdev(vdev);
 	struct rproc *rproc = vdev_to_rproc(vdev);
+	struct device *dev = &rproc->dev;
 	struct rproc_vring *rvring;
 	struct virtqueue *vq;
 	void *addr;
@@ -95,7 +96,7 @@ static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
 	size = vring_size(len, rvring->align);
 	memset(addr, 0, size);
 
-	dev_dbg(rproc->dev, "vring%d: va %p qsz %d notifyid %d\n",
+	dev_dbg(dev, "vring%d: va %p qsz %d notifyid %d\n",
 					id, addr, len, rvring->notifyid);
 
 	/*
@@ -105,7 +106,7 @@ static struct virtqueue *rp_find_vq(struct virtio_device *vdev,
 	vq = vring_new_virtqueue(len, rvring->align, vdev, false, addr,
 					rproc_virtio_notify, callback, name);
 	if (!vq) {
-		dev_err(rproc->dev, "vring_new_virtqueue %s failed\n", name);
+		dev_err(dev, "vring_new_virtqueue %s failed\n", name);
 		rproc_free_vring(rvring);
 		return ERR_PTR(-ENOMEM);
 	}
@@ -152,7 +153,7 @@ static int rproc_virtio_find_vqs(struct virtio_device *vdev, unsigned nvqs,
 	/* now that the vqs are all set, boot the remote processor */
 	ret = rproc_boot(rproc);
 	if (ret) {
-		dev_err(rproc->dev, "rproc_boot() failed %d\n", ret);
+		dev_err(&rproc->dev, "rproc_boot() failed %d\n", ret);
 		goto error;
 	}
 
@@ -254,7 +255,7 @@ static void rproc_vdev_release(struct device *dev)
 int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id)
 {
 	struct rproc *rproc = rvdev->rproc;
-	struct device *dev = rproc->dev;
+	struct device *dev = &rproc->dev;
 	struct virtio_device *vdev = &rvdev->vdev;
 	int ret;