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From:   Divin Raj <divin.raj@arm.com>
To:     Bjorn Andersson <andersson@kernel.org>,
        Mathieu Poirier <mathieu.poirier@linaro.org>
Cc:     linux-kernel@vger.kernel.org, linux-remoteproc@vger.kernel.org,
        Peter Hoyes <Peter.Hoyes@arm.com>
Subject: [PATCH 1/1] rpmsg: virtio: Make buffer size and number configurable
Date:   Thu, 28 Sep 2023 16:38:25 +0100
Message-Id: <20230928153825.151948-2-divin.raj@arm.com>
In-Reply-To: <20230928153825.151948-1-divin.raj@arm.com>
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From: Peter Hoyes <Peter.Hoyes@arm.com>

Replace the MAX_RPMSG_BUF_SIZE and MAX_RPMSG_NUM_BUFS #define in
virtio_rpmsg_bus.c with the Kconfig parameters CONFIG_RPMSG_VIRTIO_BUF_SIZE
and CONFIG_RPMSG_VIRTIO_MAX_NUM_BUFS, allowing user-provided customization.

Making both the number of buffers and size configurable facilitates aligning
memory requirements between vdev-buffer and vdev-vrings for client drivers
that require larger buffer sizes, for example.

Signed-off-by: Peter Hoyes <Peter.Hoyes@arm.com>
Signed-off-by: Divin Raj <divin.raj@arm.com>
---
 drivers/rpmsg/Kconfig            | 23 +++++++++++++++++++++++
 drivers/rpmsg/virtio_rpmsg_bus.c | 27 +++------------------------
 2 files changed, 26 insertions(+), 24 deletions(-)

diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
index d3795860f5c0..677f4a1ac8bb 100644
--- a/drivers/rpmsg/Kconfig
+++ b/drivers/rpmsg/Kconfig
@@ -81,4 +81,27 @@ config RPMSG_VIRTIO
 	select RPMSG_NS
 	select VIRTIO
 
+config RPMSG_VIRTIO_MAX_BUF_SIZE
+	int "Virtio RPMSG max buffer size (in bytes)"
+	default 512
+	depends on RPMSG_VIRTIO
+	help
+	  This option allows you to configure the maximum buffer size (in bytes)
+	  for Virtio RPMSG communications. The number of buffers will be computed
+	  based on the number of buffers (CONFIG_RPMSG_VIRTIO_MAX_NUM_BUFS)
+	  supported by the vring. By default, it supports up to a maximum of 512
+	  buffers (256 in each direction). Each buffer consists of 16 bytes for the
+	  message header and the remaining bytes for the payload.The default values
+	  will utilize a maximum total space of 256KB for the buffers.
+
+config RPMSG_VIRTIO_MAX_NUM_BUFS
+	int "Virtio RPMSG max buffer count (even number for TX and Rx)"
+	default 512
+	depends on RPMSG_VIRTIO
+	help
+	  This option allows you to configure the maximum number of buffers used
+	  for Virtio RPMSG communication. By default, it supports up to a maximum
+	  of 512 buffers (256 in each direction). Please note that this value
+	  should be an even number, as it accounts for both transmit (TX) and
+	  receive (Rx) buffers.
 endmenu
diff --git a/drivers/rpmsg/virtio_rpmsg_bus.c b/drivers/rpmsg/virtio_rpmsg_bus.c
index 905ac7910c98..87a9a4fa30e0 100644
--- a/drivers/rpmsg/virtio_rpmsg_bus.c
+++ b/drivers/rpmsg/virtio_rpmsg_bus.c
@@ -109,27 +109,6 @@ struct virtio_rpmsg_channel {
 #define to_virtio_rpmsg_channel(_rpdev) \
 	container_of(_rpdev, struct virtio_rpmsg_channel, rpdev)
 
-/*
- * 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 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
- * to achieve zero-copy messaging.
- *
- * Note that these numbers are purely a decision of this driver - we
- * can change this without changing anything in the firmware of the remote
- * processor.
- */
-#define MAX_RPMSG_NUM_BUFS	(512)
-#define MAX_RPMSG_BUF_SIZE	(512)
-
 /*
  * Local addresses are dynamically allocated on-demand.
  * We do not dynamically assign addresses from the low 1024 range,
@@ -902,12 +881,12 @@ static int rpmsg_probe(struct virtio_device *vdev)
 		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)
+	if (virtqueue_get_vring_size(vrp->rvq) < CONFIG_RPMSG_VIRTIO_MAX_NUM_BUFS / 2)
 		vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
 	else
-		vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
+		vrp->num_bufs = CONFIG_RPMSG_VIRTIO_MAX_NUM_BUFS;
 
-	vrp->buf_size = MAX_RPMSG_BUF_SIZE;
+	vrp->buf_size = CONFIG_RPMSG_VIRTIO_MAX_BUF_SIZE;
 
 	total_buf_space = vrp->num_bufs * vrp->buf_size;
 
-- 
2.25.1