linux-kernel - [PATCH 1/3] rpmsg: virtio_rpmsg_bus: allow the different vring size for send/recv

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Date:   Thu, 31 Jan 2019 23:41:18 +0800
From:   Xiang Xiao <xiaoxiang781216@...il.com>
To:     ohad@...ery.com, bjorn.andersson@...aro.org,
        wendy.liang@...inx.com, arnaud.pouliquen@...com,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Xiang Xiao <xiaoxiang@...omi.com>
Subject: [PATCH 1/3] rpmsg: virtio_rpmsg_bus: allow the different vring size for send/recv

it's useful if the communication throughput is different from each side

Signed-off-by: Xiang Xiao <xiaoxiang@...omi.com>
---
 drivers/rpmsg/virtio_rpmsg_bus.c | 47 ++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 664f957..fb0d2eb 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -36,8 +36,9 @@
  * @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
- * @buf_size:   size of one rx or tx buffer
+ * @num_rbufs:	total number of buffers for rx
+ * @num_sbufs:	total number of buffers for tx
+ * @buf_size:	size of one rx or tx buffer
  * @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.
@@ -57,7 +58,8 @@ struct virtproc_info {
 	struct virtio_device *vdev;
 	struct virtqueue *rvq, *svq;
 	void *rbufs, *sbufs;
-	unsigned int num_bufs;
+	unsigned int num_rbufs;
+	unsigned int num_sbufs;
 	unsigned int buf_size;
 	int last_sbuf;
 	dma_addr_t bufs_dma;
@@ -136,7 +138,7 @@ struct virtio_rpmsg_channel {
 /*
  * 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).
+ * by the vring, up to a maximum of 256 in each direction.
  *
  * Each buffer will have 16 bytes for the msg header and 496 bytes for
  * the payload.
@@ -151,7 +153,7 @@ struct virtio_rpmsg_channel {
  * can change this without changing anything in the firmware of the remote
  * processor.
  */
-#define MAX_RPMSG_NUM_BUFS	(512)
+#define MAX_RPMSG_NUM_BUFS	(256)
 #define MAX_RPMSG_BUF_SIZE	(512)
 
 /*
@@ -446,11 +448,8 @@ static void *get_a_tx_buf(struct virtproc_info *vrp)
 	/* support multiple concurrent senders */
 	mutex_lock(&vrp->tx_lock);
 
-	/*
-	 * either pick the next unused tx buffer
-	 * (half of our buffers are used for sending messages)
-	 */
-	if (vrp->last_sbuf < vrp->num_bufs / 2)
+	/* either pick the next unused tx buffer */
+	if (vrp->last_sbuf < vrp->num_sbufs)
 		ret = vrp->sbufs + vrp->buf_size * vrp->last_sbuf++;
 	/* or recycle a used one */
 	else
@@ -897,19 +896,20 @@ 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;
+	if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS)
+		vrp->num_rbufs = virtqueue_get_vring_size(vrp->rvq);
+	else
+		vrp->num_rbufs = MAX_RPMSG_NUM_BUFS;
+
+	if (virtqueue_get_vring_size(vrp->svq) < MAX_RPMSG_NUM_BUFS)
+		vrp->num_sbufs = virtqueue_get_vring_size(vrp->svq);
 	else
-		vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
+		vrp->num_sbufs = MAX_RPMSG_NUM_BUFS;
 
 	vrp->buf_size = MAX_RPMSG_BUF_SIZE;
 
-	total_buf_space = vrp->num_bufs * vrp->buf_size;
+	total_buf_space = (vrp->num_rbufs + vrp->num_sbufs) * vrp->buf_size;
 
 	/* allocate coherent memory for the buffers */
 	bufs_va = dma_alloc_coherent(vdev->dev.parent->parent,
@@ -923,14 +923,14 @@ static int rpmsg_probe(struct virtio_device *vdev)
 	dev_dbg(&vdev->dev, "buffers: va %p, dma %pad\n",
 		bufs_va, &vrp->bufs_dma);
 
-	/* half of the buffers is dedicated for RX */
+	/* first part of the buffers is dedicated for RX */
 	vrp->rbufs = bufs_va;
 
-	/* and half is dedicated for TX */
-	vrp->sbufs = bufs_va + total_buf_space / 2;
+	/* and second part is dedicated for TX */
+	vrp->sbufs = bufs_va + vrp->num_rbufs * vrp->buf_size;
 
 	/* set up the receive buffers */
-	for (i = 0; i < vrp->num_bufs / 2; i++) {
+	for (i = 0; i < vrp->num_rbufs; i++) {
 		struct scatterlist sg;
 		void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
 
@@ -999,7 +999,8 @@ 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 * vrp->buf_size;
+	unsigned int num_bufs = vrp->num_rbufs + vrp->num_sbufs;
+	size_t total_buf_space = num_bufs * vrp->buf_size;
 	int ret;
 
 	vdev->config->reset(vdev);
-- 
2.7.4