Merge tag 'rpmsg-3.19-next' of git://git.kernel.org/pub/scm/linux/kernel/git/ohad/rpmsg

Pull rpmsg update from Ohad Ben-Cohen:
 "A single patch from Suman Anna which makes rpmsg use less buffers when
  small vrings are being used"

* tag 'rpmsg-3.19-next' of git://git.kernel.org/pub/scm/linux/kernel/git/ohad/rpmsg:
  rpmsg: use less buffers when vrings are small

drivers/rpmsg/virtio_rpmsg_bus.c

@@ -41,6 +41,7 @@
  * @svq:	tx virtqueue
  * @rbufs:	kernel address of rx buffers
  * @sbufs:	kernel address of tx buffers
+ * @num_bufs:	total number of buffers for rx and tx
  * @last_sbuf:	index of last tx buffer used
  * @bufs_dma:	dma base addr of the buffers
  * @tx_lock:	protects svq, sbufs and sleepers, to allow concurrent senders.
@@ -60,6 +61,7 @@ struct virtproc_info {
 	struct virtio_device *vdev;
 	struct virtqueue *rvq, *svq;
 	void *rbufs, *sbufs;
+	unsigned int num_bufs;
 	int last_sbuf;
 	dma_addr_t bufs_dma;
 	struct mutex tx_lock;
@@ -86,13 +88,14 @@ struct rpmsg_channel_info {
 #define to_rpmsg_driver(d) container_of(d, struct rpmsg_driver, drv)
 
 /*
- * We're allocating 512 buffers of 512 bytes for communications, and then
- * using the first 256 buffers for RX, and the last 256 buffers for TX.
+ * We're allocating buffers of 512 bytes each for communications. The
+ * number of buffers will be computed from the number of buffers supported
+ * by the vring, upto a maximum of 512 buffers (256 in each direction).
  *
  * Each buffer will have 16 bytes for the msg header and 496 bytes for
  * the payload.
  *
- * This will require a total space of 256KB for the buffers.
+ * This will utilize a maximum total space of 256KB for the buffers.
  *
  * We might also want to add support for user-provided buffers in time.
  * This will allow bigger buffer size flexibility, and can also be used
@@ -102,9 +105,8 @@ struct rpmsg_channel_info {
  * can change this without changing anything in the firmware of the remote
  * processor.
  */
-#define RPMSG_NUM_BUFS		(512)
+#define MAX_RPMSG_NUM_BUFS	(512)
 #define RPMSG_BUF_SIZE		(512)
-#define RPMSG_TOTAL_BUF_SPACE	(RPMSG_NUM_BUFS * RPMSG_BUF_SIZE)
 
 /*
  * Local addresses are dynamically allocated on-demand.
@@ -579,7 +581,7 @@ static void *get_a_tx_buf(struct virtproc_info *vrp)
 	 * either pick the next unused tx buffer
 	 * (half of our buffers are used for sending messages)
 	 */
-	if (vrp->last_sbuf < RPMSG_NUM_BUFS / 2)
+	if (vrp->last_sbuf < vrp->num_bufs / 2)
 		ret = vrp->sbufs + RPMSG_BUF_SIZE * vrp->last_sbuf++;
 	/* or recycle a used one */
 	else
@@ -948,6 +950,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
 	struct virtproc_info *vrp;
 	void *bufs_va;
 	int err = 0, i;
+	size_t total_buf_space;
 
 	vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);
 	if (!vrp)
@@ -968,10 +971,22 @@ static int rpmsg_probe(struct virtio_device *vdev)
 	vrp->rvq = vqs[0];
 	vrp->svq = vqs[1];
 
+	/* we expect symmetric tx/rx vrings */
+	WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
+		virtqueue_get_vring_size(vrp->svq));
+
+	/* we need less buffers if vrings are small */
+	if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
+		vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
+	else
+		vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
+
+	total_buf_space = vrp->num_bufs * RPMSG_BUF_SIZE;
+
 	/* allocate coherent memory for the buffers */
 	bufs_va = dma_alloc_coherent(vdev->dev.parent->parent,
-				RPMSG_TOTAL_BUF_SPACE,
-				&vrp->bufs_dma, GFP_KERNEL);
+				     total_buf_space, &vrp->bufs_dma,
+				     GFP_KERNEL);
 	if (!bufs_va) {
 		err = -ENOMEM;
 		goto vqs_del;
@@ -984,10 +999,10 @@ static int rpmsg_probe(struct virtio_device *vdev)
 	vrp->rbufs = bufs_va;
 
 	/* and half is dedicated for TX */
-	vrp->sbufs = bufs_va + RPMSG_TOTAL_BUF_SPACE / 2;
+	vrp->sbufs = bufs_va + total_buf_space / 2;
 
 	/* set up the receive buffers */
-	for (i = 0; i < RPMSG_NUM_BUFS / 2; i++) {
+	for (i = 0; i < vrp->num_bufs / 2; i++) {
 		struct scatterlist sg;
 		void *cpu_addr = vrp->rbufs + i * RPMSG_BUF_SIZE;
 
@@ -1023,7 +1038,7 @@ static int rpmsg_probe(struct virtio_device *vdev)
 	return 0;
 
 free_coherent:
-	dma_free_coherent(vdev->dev.parent->parent, RPMSG_TOTAL_BUF_SPACE,
+	dma_free_coherent(vdev->dev.parent->parent, total_buf_space,
 			  bufs_va, vrp->bufs_dma);
 vqs_del:
 	vdev->config->del_vqs(vrp->vdev);
@@ -1042,6 +1057,7 @@ static int rpmsg_remove_device(struct device *dev, void *data)
 static void rpmsg_remove(struct virtio_device *vdev)
 {
 	struct virtproc_info *vrp = vdev->priv;
+	size_t total_buf_space = vrp->num_bufs * RPMSG_BUF_SIZE;
 	int ret;
 
 	vdev->config->reset(vdev);
@@ -1057,7 +1073,7 @@ static void rpmsg_remove(struct virtio_device *vdev)
 
 	vdev->config->del_vqs(vrp->vdev);
 
-	dma_free_coherent(vdev->dev.parent->parent, RPMSG_TOTAL_BUF_SPACE,
+	dma_free_coherent(vdev->dev.parent->parent, total_buf_space,
 			  vrp->rbufs, vrp->bufs_dma);
 
 	kfree(vrp);