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Message-ID: <d1f07248-194b-429c-aceb-9d586aad934b@foss.st.com>
Date: Fri, 21 Nov 2025 10:40:15 +0100
From: Arnaud POULIQUEN <arnaud.pouliquen@...s.st.com>
To: Tanmay Shah <tanmay.shah@....com>, <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>
Subject: Re: [RFC PATCH 1/2] rpmsg: virtio_rpmsg_bus: allow the different
vring size for send/recv
Hi Tanmay,
On 11/14/25 19:46, Tanmay Shah wrote:
> 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>
Thanks you for reopening of this series!
> ---
> 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
Nitpicking... I wonder if rx, tx term would be more generic
In such case s/num_rxbufs/n_rx_buf/ s/num_sbufs/num_txbufs/
Regards
Arnaud
> + * @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);
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