Re: [PATCH v10 07/26] mailbox: Add Gunyah message queue mailbox
From: Elliot Berman
Date: Wed Feb 22 2023 - 19:15:41 EST
On 2/20/2023 5:59 AM, Srinivas Kandagatla wrote:
On 14/02/2023 21:23, Elliot Berman wrote:
Gunyah message queues are a unidirectional inter-VM pipe for messages up
to 1024 bytes. This driver supports pairing a receiver message queue and
a transmitter message queue to expose a single mailbox channel.
Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
Documentation/virt/gunyah/message-queue.rst | 8 +
drivers/mailbox/Makefile | 2 +
drivers/mailbox/gunyah-msgq.c | 214 ++++++++++++++++++++
include/linux/gunyah.h | 56 +++++
4 files changed, 280 insertions(+)
create mode 100644 drivers/mailbox/gunyah-msgq.c
diff --git a/Documentation/virt/gunyah/message-queue.rst
b/Documentation/virt/gunyah/message-queue.rst
index 0667b3eb1ff9..082085e981e0 100644
--- a/Documentation/virt/gunyah/message-queue.rst
+++ b/Documentation/virt/gunyah/message-queue.rst
@@ -59,3 +59,11 @@ vIRQ: two TX message queues will have two vIRQs
(and two capability IDs).
| | | |
| |
| | | |
| |
+---------------+ +-----------------+
+---------------+
+
+Gunyah message queues are exposed as mailboxes. To create the
mailbox, create
+a mbox_client and call `gh_msgq_init`. On receipt of the RX_READY
interrupt,
+all messages in the RX message queue are read and pushed via the
`rx_callback`
+of the registered mbox_client.
+
+.. kernel-doc:: drivers/mailbox/gunyah-msgq.c
+ :identifiers: gh_msgq_init
diff --git a/drivers/mailbox/Makefile b/drivers/mailbox/Makefile
index fc9376117111..5f929bb55e9a 100644
--- a/drivers/mailbox/Makefile
+++ b/drivers/mailbox/Makefile
@@ -55,6 +55,8 @@ obj-$(CONFIG_MTK_CMDQ_MBOX) += mtk-cmdq-mailbox.o
obj-$(CONFIG_ZYNQMP_IPI_MBOX) += zynqmp-ipi-mailbox.o
+obj-$(CONFIG_GUNYAH) += gunyah-msgq.o
Why are we reusing CONFIG_GUNYAH Kconfig symbol for mailbox, why not
CONFIG_GUNYAH_MBOX?
There was some previous discussion about this:
https://lore.kernel.org/all/2a7bb5f2-1286-b661-659a-a5037150eae8@xxxxxxxxxxx/
+
obj-$(CONFIG_SUN6I_MSGBOX) += sun6i-msgbox.o
obj-$(CONFIG_SPRD_MBOX) += sprd-mailbox.o
diff --git a/drivers/mailbox/gunyah-msgq.c
b/drivers/mailbox/gunyah-msgq.c
new file mode 100644
index 000000000000..03ffaa30ce9b
--- /dev/null
+++ b/drivers/mailbox/gunyah-msgq.c
@@ -0,0 +1,214 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All
rights reserved.
+ */
+
+#include <linux/mailbox_controller.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/gunyah.h>
+#include <linux/printk.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/wait.h>
...
+/* Fired when message queue transitions from "full" to "space
available" to send messages */
+static irqreturn_t gh_msgq_tx_irq_handler(int irq, void *data)
+{
+ struct gh_msgq *msgq = data;
+
+ mbox_chan_txdone(gh_msgq_chan(msgq), 0);
+
+ return IRQ_HANDLED;
+}
+
+/* Fired after sending message and hypercall told us there was more
space available. */
+static void gh_msgq_txdone_tasklet(struct tasklet_struct *tasklet)
Tasklets have been long deprecated, consider using workqueues in this
particular case.
Workqueues have higher latency and tasklets came as recommendation from
Jassi. drivers/mailbox/imx-mailbox.c uses tasklets in the same way.
I did some quick unscientific measurements of ~1000x samples. The median
latency for resource manager went from 25.5 us (tasklet) to 26 us
(workqueue) (2% slower). The mean went from 28.7 us to 32.5 us (13%
slower). Obviously, the outliers for workqueues were much more extreme.
+{
+ struct gh_msgq *msgq = container_of(tasklet, struct gh_msgq,
txdone_tasklet);
+
+ mbox_chan_txdone(gh_msgq_chan(msgq), msgq->last_ret);
+}
+
+static int gh_msgq_send_data(struct mbox_chan *chan, void *data)
+{
..
+ tasklet_schedule(&msgq->txdone_tasklet);
+
+ return 0;
+}
+
+static struct mbox_chan_ops gh_msgq_ops = {
+ .send_data = gh_msgq_send_data,
+};
+
+/**
+ * gh_msgq_init() - Initialize a Gunyah message queue with an
mbox_client
+ * @parent: optional, device parent used for the mailbox controller
+ * @msgq: Pointer to the gh_msgq to initialize
+ * @cl: A mailbox client to bind to the mailbox channel that the
message queue creates
+ * @tx_ghrsc: optional, the transmission side of the message queue
+ * @rx_ghrsc: optional, the receiving side of the message queue
+ *
+ * At least one of tx_ghrsc and rx_ghrsc should be not NULL. Most
message queue use cases come with
+ * a pair of message queues to facilitate bidirectional
communication. When tx_ghrsc is set,
+ * the client can send messages with
mbox_send_message(gh_msgq_chan(msgq), msg). When rx_ghrsc
+ * is set, the mbox_client should register an .rx_callback() and the
message queue driver will
+ * push all available messages upon receiving the RX ready interrupt.
The messages should be
+ * consumed or copied by the client right away as the gh_msgq_rx_data
will be replaced/destroyed
+ * after the callback.
+ *
+ * Returns - 0 on success, negative otherwise
+ */
+int gh_msgq_init(struct device *parent, struct gh_msgq *msgq, struct
mbox_client *cl,
+ struct gunyah_resource *tx_ghrsc, struct gunyah_resource
*rx_ghrsc)
+{
+ int ret;
+
+ /* Must have at least a tx_ghrsc or rx_ghrsc and that they are
the right device types */
+ if ((!tx_ghrsc && !rx_ghrsc) ||
+ (tx_ghrsc && tx_ghrsc->type != GUNYAH_RESOURCE_TYPE_MSGQ_TX) ||
+ (rx_ghrsc && rx_ghrsc->type != GUNYAH_RESOURCE_TYPE_MSGQ_RX))
+ return -EINVAL;
+
+ if (gh_api_version() != GUNYAH_API_V1) {
+ pr_err("Unrecognized gunyah version: %u. Currently supported:
%d\n",
dev_err(parent
would make this more useful
Done.
- Elliot