[PATCH v4 09/14] 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>
---
 MAINTAINERS                   |   2 +
 drivers/mailbox/Kconfig       |  10 ++
 drivers/mailbox/Makefile      |   2 +
 drivers/mailbox/gunyah-msgq.c | 232 ++++++++++++++++++++++++++++++++++
 drivers/virt/gunyah/Kconfig   |   2 +
 include/linux/gunyah.h        |  67 ++++++++++
 6 files changed, 315 insertions(+)
 create mode 100644 drivers/mailbox/gunyah-msgq.c
 create mode 100644 include/linux/gunyah.h

diff --git a/MAINTAINERS b/MAINTAINERS
index a26e67ef36b4..74053d8ff7ea 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -8889,8 +8889,10 @@ F:	Documentation/ABI/testing/sysfs-hypervisor-gunyah
 F:	Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
 F:	Documentation/virt/gunyah/
 F:	arch/arm64/gunyah/
+F:	drivers/mailbox/gunyah-msgq.c
 F:	drivers/virt/gunyah/
 F:	include/asm-generic/gunyah.h
+F:	include/linux/gunyah.h
 
 HABANALABS PCI DRIVER
 M:	Oded Gabbay <ogabbay@kernel.org>
diff --git a/drivers/mailbox/Kconfig b/drivers/mailbox/Kconfig
index 05d6fae800e3..baf9451c5f04 100644
--- a/drivers/mailbox/Kconfig
+++ b/drivers/mailbox/Kconfig
@@ -41,6 +41,16 @@ config IMX_MBOX
 	help
 	  Mailbox implementation for i.MX Messaging Unit (MU).
 
+config GUNYAH_MESSAGE_QUEUES
+	tristate "Gunyah Message Queue Mailbox"
+	depends on GUNYAH
+	help
+	  Mailbox implementation for Gunyah Message Queues. Gunyah message queues
+	  are an IPC mechanism to pass short messages between virtual machines
+	  running under the Gunyah hypervisor.
+
+	  Say Y here if you run Linux as a Gunyah virtual machine.
+
 config PLATFORM_MHU
 	tristate "Platform MHU Mailbox"
 	depends on OF
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..359f682d101c
--- /dev/null
+++ b/drivers/mailbox/gunyah-msgq.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/mailbox_controller.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 gunyah_msgq, mbox))
+
+static inline bool gh_msgq_has_tx(struct gunyah_msgq *msgq)
+{
+	return msgq->tx_ghrsc.type == GUNYAH_RESOURCE_TYPE_MSGQ_TX;
+}
+
+static inline bool gh_msgq_has_rx(struct gunyah_msgq *msgq)
+{
+	return msgq->rx_ghrsc.type == GUNYAH_RESOURCE_TYPE_MSGQ_RX;
+}
+
+static ssize_t __gh_msgq_recv(struct gunyah_msgq *msgq, void *buff, size_t size, bool *ready)
+{
+	unsigned long gh_err;
+	size_t recv_size;
+	ssize_t ret;
+
+	gh_err = gh_hypercall_msgq_recv(msgq->rx_ghrsc.capid, (uintptr_t)buff, size,
+					&recv_size, ready);
+	switch (gh_err) {
+	case GH_ERROR_OK:
+		ret = recv_size;
+		break;
+	case GH_ERROR_MSGQUEUE_EMPTY:
+		ret = -EAGAIN;
+		*ready = false;
+		break;
+	default:
+		ret = gh_remap_error(gh_err);
+		break;
+	}
+
+	return ret;
+}
+
+static irqreturn_t gh_msgq_rx_irq_handler(int irq, void *data)
+{
+	struct gunyah_msgq *msgq = data;
+	struct gunyah_msgq_rx_data rx_data;
+	ssize_t ret;
+	bool more;
+
+	do {
+		ret = __gh_msgq_recv(msgq, &rx_data.data, sizeof(rx_data.data), &more);
+
+		if (ret >= 0) {
+			rx_data.length = ret;
+			mbox_chan_received_data(gunyah_msgq_chan(msgq), &rx_data);
+		} else if (ret != -EAGAIN)
+			pr_warn("Failed to receive data from msgq for %s: %ld\n",
+				msgq->mbox.dev ? dev_name(msgq->mbox.dev) : "", ret);
+	} while (ret >= 0 && more);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t gh_msgq_tx_irq_handler(int irq, void *data)
+{
+	struct gunyah_msgq *msgq = data;
+
+	mbox_chan_txdone(gunyah_msgq_chan(msgq), 0);
+
+	return IRQ_HANDLED;
+}
+
+static void gh_msgq_txdone_tasklet(unsigned long data)
+{
+	struct gunyah_msgq *msgq = (struct gunyah_msgq *)data;
+
+	mbox_chan_txdone(gunyah_msgq_chan(msgq), msgq->last_status);
+}
+
+static int __gh_msgq_send(struct gunyah_msgq *msgq, void *buff, size_t size, u64 tx_flags)
+{
+	unsigned long gh_err;
+	ssize_t ret;
+	bool ready;
+
+	gh_err = gh_hypercall_msgq_send(msgq->tx_ghrsc.capid, size, (uintptr_t)buff, tx_flags,
+					&ready);
+	switch (gh_err) {
+	case GH_ERROR_OK:
+		ret = !ready;
+		break;
+	case GH_ERROR_MSGQUEUE_FULL:
+		ret = -EAGAIN;
+		break;
+	default:
+		/* Not sure how to propagate these out to client. If we get here, nobody is going
+		 * to trigger a retry
+		 */
+		ret = gh_remap_error(gh_err);
+		break;
+	}
+
+	return ret;
+}
+
+static int gh_msgq_send_data(struct mbox_chan *chan, void *data)
+{
+	struct gunyah_msgq *msgq = mbox_chan_to_msgq(chan);
+	struct gunyah_msgq_tx_data *msgq_data = data;
+	u64 tx_flags = 0;
+	int ret;
+
+	if (msgq_data->push)
+		tx_flags |= GH_HYPERCALL_MSGQ_TX_FLAGS_PUSH;
+
+	ret = __gh_msgq_send(msgq, msgq_data->data, msgq_data->length, tx_flags);
+
+	/**
+	 * EAGAIN: message didn't send.
+	 * ret = 1: message sent, but now the message queue is full and we can't send any more msgs.
+	 * Either way, don't report that this message is done.
+	 */
+	if (ret == -EAGAIN || ret == 1)
+		return ret;
+
+	/**
+	 * Mailbox framework requires that tx done happens asynchronously to sending the message
+	 * IOW, a notification that the message was sent happens after sending the message.
+	 * To work around this, defer the txdone to a tasklet.
+	 */
+	msgq->last_status = ret;
+	tasklet_schedule(&msgq->txdone_tasklet);
+
+	return 0;
+}
+
+struct mbox_chan_ops gunyah_msgq_ops = {
+	.send_data = gh_msgq_send_data,
+};
+
+/**
+ * gunyah_msgq_init() - Initialize a Gunyah message queue with an mbox_client
+ * @parent: optional, device parent used for the mailbox controller
+ * @msgq: Pointer to the gunyah_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 facilitiate bidirectional communication. When tx_ghrsc is set,
+ * the client can send messages with mbox_send_message(gunyah_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 gunyah_msgq_rx_data will be replaced/destroyed
+ * after the callback.
+ *
+ * Returns - 0 on success, negative otherwise
+ */
+int gunyah_msgq_init(struct device *parent, struct gunyah_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;
+
+	msgq->tx_ghrsc = *tx_ghrsc;
+	msgq->rx_ghrsc = *rx_ghrsc;
+
+	msgq->mbox.dev = parent;
+	msgq->mbox.ops = &gunyah_msgq_ops;
+	msgq->mbox.chans = kcalloc(1, sizeof(*msgq->mbox.chans), GFP_KERNEL);
+	msgq->mbox.num_chans = 1;
+	msgq->mbox.txdone_irq = true;
+
+	if (gh_msgq_has_tx(msgq)) {
+		ret = request_irq(msgq->tx_ghrsc.irq, gh_msgq_tx_irq_handler, 0, "gh_msgq_tx",
+				msgq);
+		if (ret)
+			goto err_chans;
+	}
+
+	if (gh_msgq_has_rx(msgq)) {
+		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;
+	}
+
+	tasklet_init(&msgq->txdone_tasklet, gh_msgq_txdone_tasklet, (unsigned long)msgq);
+
+	ret = mbox_controller_register(&msgq->mbox);
+	if (ret)
+		goto err_rx_irq;
+
+	ret = mbox_bind_client(gunyah_msgq_chan(msgq), cl);
+	if (ret)
+		goto err_mbox;
+
+	return 0;
+err_mbox:
+	mbox_controller_unregister(&msgq->mbox);
+err_rx_irq:
+	if (gh_msgq_has_rx(msgq))
+		free_irq(msgq->rx_ghrsc.irq, msgq);
+err_tx_irq:
+	if (gh_msgq_has_tx(msgq))
+		free_irq(msgq->tx_ghrsc.irq, msgq);
+err_chans:
+	kfree(msgq->mbox.chans);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(gunyah_msgq_init);
+
+void gunyah_msgq_remove(struct gunyah_msgq *msgq)
+{
+	if (gh_msgq_has_tx(msgq))
+		free_irq(msgq->tx_ghrsc.irq, msgq);
+
+	kfree(msgq->mbox.chans);
+}
+EXPORT_SYMBOL_GPL(gunyah_msgq_remove);
diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
index 7ac917e0aa3f..f4c822a82f1a 100644
--- a/drivers/virt/gunyah/Kconfig
+++ b/drivers/virt/gunyah/Kconfig
@@ -4,6 +4,8 @@ config GUNYAH
 	tristate "Gunyah Virtualization drivers"
 	depends on ARM64
 	select AUXILIARY_BUS
+	select MAILBOX
+	select GUNYAH_MESSAGE_QUEUES
 	help
 	  The Gunyah drivers are the helper interfaces that runs in a guest VM
 	  such as basic inter-VM IPC and signaling mechanisms, and higher level
diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
new file mode 100644
index 000000000000..d5e80e2defab
--- /dev/null
+++ b/include/linux/gunyah.h
@@ -0,0 +1,67 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#ifndef _GUNYAH_H
+#define _GUNYAH_H
+
+#include <linux/mailbox_controller.h>
+#include <linux/mailbox_client.h>
+#include <linux/interrupt.h>
+
+#include <asm-generic/gunyah.h>
+
+/* Follows resource manager's resource types for VM_GET_HYP_RESOURCES */
+enum gunyah_resource_type {
+	GUNYAH_RESOURCE_TYPE_BELL_TX	= 0,
+	GUNYAH_RESOURCE_TYPE_BELL_RX	= 1,
+	GUNYAH_RESOURCE_TYPE_MSGQ_TX	= 2,
+	GUNYAH_RESOURCE_TYPE_MSGQ_RX	= 3,
+	GUNYAH_RESOURCE_TYPE_VCPU	= 4,
+};
+
+struct gunyah_resource {
+	enum gunyah_resource_type type;
+	u64 capid;
+	int irq;
+};
+
+/**
+ * Gunyah Message Queues
+ */
+
+#define GH_MSGQ_MAX_MSG_SIZE	1024
+
+struct gunyah_msgq_tx_data {
+	size_t length;
+	bool push;
+	char data[];
+};
+
+struct gunyah_msgq_rx_data {
+	size_t length;
+	char data[GH_MSGQ_MAX_MSG_SIZE];
+};
+
+struct gunyah_msgq {
+	struct gunyah_resource tx_ghrsc;
+	struct gunyah_resource rx_ghrsc;
+
+	/* msgq private */
+	int last_status;
+	struct mbox_controller mbox;
+	struct tasklet_struct txdone_tasklet;
+};
+
+
+int gunyah_msgq_init(struct device *parent, struct gunyah_msgq *msgq, struct mbox_client *cl,
+		     struct gunyah_resource *tx_ghrsc, struct gunyah_resource *rx_ghrsc);
+void gunyah_msgq_remove(struct gunyah_msgq *msgq);
+
+static inline struct mbox_chan *gunyah_msgq_chan(struct gunyah_msgq *msgq)
+{
+	return &msgq->mbox.chans[0];
+}
+
+#endif
-- 
2.25.1