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Message-ID: <20251114184640.3020427-2-tanmay.shah@amd.com>
Date: Fri, 14 Nov 2025 10:46:39 -0800
From: Tanmay Shah <tanmay.shah@....com>
To: <andersson@...nel.org>, <mathieu.poirier@...aro.org>, <mst@...hat.com>,
<jasowang@...hat.com>, <xuanzhuo@...ux.alibaba.com>, <eperezma@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <linux-remoteproc@...r.kernel.org>,
<virtualization@...ts.linux.dev>, <xiaoxiang@...omi.com>, Xiang Xiao
<xiaoxiang781216@...il.com>, Tanmay Shah <tanmay.shah@....com>
Subject: [RFC PATCH 1/2] rpmsg: virtio_rpmsg_bus: allow the different vring size for send/recv
From: Xiang Xiao <xiaoxiang781216@...il.com>
it's useful if the communication throughput is different from each side
Signed-off-by: Xiang Xiao <xiaoxiang@...omi.com>
Signed-off-by: Tanmay Shah <tanmay.shah@....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 484890b4a6a7..cc26dfcc3e29 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -37,8 +37,9 @@
* @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;
@@ -112,7 +114,7 @@ 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.
@@ -127,7 +129,7 @@ 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)
/*
@@ -439,11 +441,8 @@ 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
@@ -878,19 +877,20 @@ 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,
@@ -904,14 +904,14 @@ 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;
@@ -1001,7 +1001,8 @@ 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;
virtio_reset_device(vdev);
--
2.34.1
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