[PATCH v13 05/24] mailbox: Add Gunyah message queue mailbox

[Elliot Berman <quic_eberman@quicinc.com>]

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@quicinc.com>
---
 Documentation/virt/gunyah/message-queue.rst |   8 +
 drivers/mailbox/Makefile                    |   2 +
 drivers/mailbox/gunyah-msgq.c               | 212 ++++++++++++++++++++
 include/linux/gunyah.h                      |  57 ++++++
 4 files changed, 279 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 b352918ae54b..70d82a4ef32d 100644
--- a/Documentation/virt/gunyah/message-queue.rst
+++ b/Documentation/virt/gunyah/message-queue.rst
@@ -61,3 +61,11 @@ 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-$(CONFIG_GUNYAH)		+= gunyah-msgq.o
+
 obj-$(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..b7a54f233680
--- /dev/null
+++ b/drivers/mailbox/gunyah-msgq.c
@@ -0,0 +1,212 @@
+// 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>
+
+#define mbox_chan_to_msgq(chan) (container_of(chan->mbox, struct gh_msgq, mbox))
+
+static irqreturn_t gh_msgq_rx_irq_handler(int irq, void *data)
+{
+	struct gh_msgq *msgq = data;
+	struct gh_msgq_rx_data rx_data;
+	enum gh_error gh_error;
+	bool ready = true;
+
+	while (ready) {
+		gh_error = gh_hypercall_msgq_recv(msgq->rx_ghrsc->capid,
+				&rx_data.data, sizeof(rx_data.data),
+				&rx_data.length, &ready);
+		if (gh_error != GH_ERROR_OK) {
+			if (gh_error != GH_ERROR_MSGQUEUE_EMPTY)
+				dev_warn(msgq->mbox.dev, "Failed to receive data: %d\n", gh_error);
+			break;
+		}
+		if (likely(gh_msgq_chan(msgq)->cl))
+			mbox_chan_received_data(gh_msgq_chan(msgq), &rx_data);
+	}
+
+	return IRQ_HANDLED;
+}
+
+/* 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)
+{
+	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)
+{
+	struct gh_msgq *msgq = mbox_chan_to_msgq(chan);
+	struct gh_msgq_tx_data *msgq_data = data;
+	u64 tx_flags = 0;
+	enum gh_error gh_error;
+	bool ready;
+
+	if (!msgq->tx_ghrsc)
+		return -EOPNOTSUPP;
+
+	if (msgq_data->push)
+		tx_flags |= GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH;
+
+	gh_error = gh_hypercall_msgq_send(msgq->tx_ghrsc->capid, msgq_data->length, msgq_data->data,
+						tx_flags, &ready);
+
+	/**
+	 * unlikely because Linux tracks state of msgq and should not try to
+	 * send message when msgq is full.
+	 */
+	if (unlikely(gh_error == GH_ERROR_MSGQUEUE_FULL))
+		return -EAGAIN;
+
+	/**
+	 * Propagate all other errors to client. If we return error to mailbox
+	 * framework, then no other messages can be sent and nobody will know
+	 * to retry this message.
+	 */
+	msgq->last_ret = gh_error_remap(gh_error);
+
+	/**
+	 * This message was successfully sent, but message queue isn't ready to
+	 * accept more messages because it's now full. Mailbox framework
+	 * requires that we only report that message was transmitted when
+	 * we're ready to transmit another message. We'll get that in the form
+	 * of tx IRQ once the other side starts to drain the msgq.
+	 */
+	if (gh_error == GH_ERROR_OK) {
+		if (!ready)
+			return 0;
+	} else
+		dev_err(msgq->mbox.dev, "Failed to send data: %d (%d)\n", gh_error, msgq->last_ret);
+
+	/**
+	 * We can send more messages. Mailbox framework requires that tx done
+	 * happens asynchronously to sending the message. Gunyah message queues
+	 * tell us right away on the hypercall return whether we can send more
+	 * messages. To work around this, defer the txdone to a tasklet.
+	 */
+	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: 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 must 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 must register an .rx_callback() and the message queue driver will
+ * deliver 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 gh_resource *tx_ghrsc, struct gh_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 != GH_RESOURCE_TYPE_MSGQ_TX) ||
+	    (rx_ghrsc && rx_ghrsc->type != GH_RESOURCE_TYPE_MSGQ_RX))
+		return -EINVAL;
+
+	msgq->mbox.dev = parent;
+	msgq->mbox.ops = &gh_msgq_ops;
+	msgq->mbox.num_chans = 1;
+	msgq->mbox.txdone_irq = true;
+	msgq->mbox.chans = &msgq->mbox_chan;
+
+	ret = mbox_controller_register(&msgq->mbox);
+	if (ret)
+		return ret;
+
+	ret = mbox_bind_client(gh_msgq_chan(msgq), cl);
+	if (ret)
+		goto err_mbox;
+
+	if (tx_ghrsc) {
+		msgq->tx_ghrsc = tx_ghrsc;
+
+		ret = request_irq(msgq->tx_ghrsc->irq, gh_msgq_tx_irq_handler, 0, "gh_msgq_tx",
+				msgq);
+		if (ret)
+			goto err_tx_ghrsc;
+
+		tasklet_setup(&msgq->txdone_tasklet, gh_msgq_txdone_tasklet);
+	}
+
+	if (rx_ghrsc) {
+		msgq->rx_ghrsc = rx_ghrsc;
+
+		ret = request_threaded_irq(msgq->rx_ghrsc->irq, NULL, gh_msgq_rx_irq_handler,
+						IRQF_ONESHOT, "gh_msgq_rx", msgq);
+		if (ret)
+			goto err_tx_irq;
+	}
+
+	return 0;
+err_tx_irq:
+	if (msgq->tx_ghrsc)
+		free_irq(msgq->tx_ghrsc->irq, msgq);
+
+	msgq->rx_ghrsc = NULL;
+err_tx_ghrsc:
+	msgq->tx_ghrsc = NULL;
+err_mbox:
+	mbox_controller_unregister(&msgq->mbox);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gh_msgq_init);
+
+void gh_msgq_remove(struct gh_msgq *msgq)
+{
+	if (msgq->rx_ghrsc)
+		free_irq(msgq->rx_ghrsc->irq, msgq);
+
+	if (msgq->tx_ghrsc) {
+		tasklet_kill(&msgq->txdone_tasklet);
+		free_irq(msgq->tx_ghrsc->irq, msgq);
+	}
+
+	mbox_controller_unregister(&msgq->mbox);
+
+	msgq->rx_ghrsc = NULL;
+	msgq->tx_ghrsc = NULL;
+}
+EXPORT_SYMBOL_GPL(gh_msgq_remove);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Gunyah Message Queue Driver");
diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
index 01a6f202d037..982e27d10d57 100644
--- a/include/linux/gunyah.h
+++ b/include/linux/gunyah.h
@@ -8,11 +8,68 @@
 
 #include <linux/bitfield.h>
 #include <linux/errno.h>
+#include <linux/interrupt.h>
 #include <linux/limits.h>
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox_client.h>
 #include <linux/types.h>
 
+/* Matches resource manager's resource types for VM_GET_HYP_RESOURCES RPC */
+enum gh_resource_type {
+	GH_RESOURCE_TYPE_BELL_TX	= 0,
+	GH_RESOURCE_TYPE_BELL_RX	= 1,
+	GH_RESOURCE_TYPE_MSGQ_TX	= 2,
+	GH_RESOURCE_TYPE_MSGQ_RX	= 3,
+	GH_RESOURCE_TYPE_VCPU		= 4,
+};
+
+struct gh_resource {
+	enum gh_resource_type type;
+	u64 capid;
+	unsigned int irq;
+};
+
+/**
+ * Gunyah Message Queues
+ */
+
+#define GH_MSGQ_MAX_MSG_SIZE		240
+
+struct gh_msgq_tx_data {
+	size_t length;
+	bool push;
+	char data[];
+};
+
+struct gh_msgq_rx_data {
+	size_t length;
+	char data[GH_MSGQ_MAX_MSG_SIZE];
+};
+
+struct gh_msgq {
+	struct gh_resource *tx_ghrsc;
+	struct gh_resource *rx_ghrsc;
+
+	/* msgq private */
+	int last_ret; /* Linux error, not GH_STATUS_* */
+	struct mbox_chan mbox_chan;
+	struct mbox_controller mbox;
+	struct tasklet_struct txdone_tasklet;
+};
+
+
+int gh_msgq_init(struct device *parent, struct gh_msgq *msgq, struct mbox_client *cl,
+		     struct gh_resource *tx_ghrsc, struct gh_resource *rx_ghrsc);
+void gh_msgq_remove(struct gh_msgq *msgq);
+
+static inline struct mbox_chan *gh_msgq_chan(struct gh_msgq *msgq)
+{
+	return &msgq->mbox.chans[0];
+}
+
 /******************************************************************************/
 /* Common arch-independent definitions for Gunyah hypercalls                  */
+
 #define GH_CAPID_INVAL	U64_MAX
 #define GH_VMID_ROOT_VM	0xff
 
-- 
2.40.0