rpmsg: Introduce Qualcomm RPM glink driver

This introduces a basic driver for communicating over "native glink"
with the RPM found in Qualcomm platforms.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

3 files changed, 1244 insertions, 0 deletions

diff --git a/drivers/rpmsg/Kconfig b/drivers/rpmsg/Kconfig
index edc008f55663..2a5d2b446de2 100644
--- a/drivers/rpmsg/Kconfig
+++ b/drivers/rpmsg/Kconfig
@@ -13,6 +13,16 @@ config RPMSG_CHAR
 	  in /dev. They make it possible for user-space programs to send and
 	  receive rpmsg packets.
 
+config RPMSG_QCOM_GLINK_RPM
+	tristate "Qualcomm RPM Glink driver"
+	select RPMSG
+	depends on HAS_IOMEM
+	depends on MAILBOX
+	help
+	  Say y here to enable support for the GLINK RPM communication driver,
+	  which serves as a channel for communication with the RPM in GLINK
+	  enabled systems.
+
 config RPMSG_QCOM_SMD
 	tristate "Qualcomm Shared Memory Driver (SMD)"
 	depends on QCOM_SMEM
diff --git a/drivers/rpmsg/Makefile b/drivers/rpmsg/Makefile
index fae9a6d548fb..28cc19088cc0 100644
--- a/drivers/rpmsg/Makefile
+++ b/drivers/rpmsg/Makefile
@@ -1,4 +1,5 @@
 obj-$(CONFIG_RPMSG)		+= rpmsg_core.o
 obj-$(CONFIG_RPMSG_CHAR)	+= rpmsg_char.o
+obj-$(CONFIG_RPMSG_QCOM_GLINK_RPM) += qcom_glink_rpm.o
 obj-$(CONFIG_RPMSG_QCOM_SMD)	+= qcom_smd.o
 obj-$(CONFIG_RPMSG_VIRTIO)	+= virtio_rpmsg_bus.o
diff --git a/drivers/rpmsg/qcom_glink_rpm.c b/drivers/rpmsg/qcom_glink_rpm.c
new file mode 100644
index 000000000000..3559a3e84c1e
--- /dev/null
+++ b/drivers/rpmsg/qcom_glink_rpm.c
@@ -0,0 +1,1233 @@
+/*
+ * Copyright (c) 2016-2017, Linaro Ltd
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/idr.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/list.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/rpmsg.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/mailbox_client.h>
+
+#include "rpmsg_internal.h"
+
+#define RPM_TOC_SIZE		256
+#define RPM_TOC_MAGIC		0x67727430 /* grt0 */
+#define RPM_TOC_MAX_ENTRIES	((RPM_TOC_SIZE - sizeof(struct rpm_toc)) / \
+				 sizeof(struct rpm_toc_entry))
+
+#define RPM_TX_FIFO_ID		0x61703272 /* ap2r */
+#define RPM_RX_FIFO_ID		0x72326170 /* r2ap */
+
+#define GLINK_NAME_SIZE		32
+
+#define RPM_GLINK_CID_MIN	1
+#define RPM_GLINK_CID_MAX	65536
+
+struct rpm_toc_entry {
+	__le32 id;
+	__le32 offset;
+	__le32 size;
+} __packed;
+
+struct rpm_toc {
+	__le32 magic;
+	__le32 count;
+
+	struct rpm_toc_entry entries[];
+} __packed;
+
+struct glink_msg {
+	__le16 cmd;
+	__le16 param1;
+	__le32 param2;
+	u8 data[];
+} __packed;
+
+struct glink_rpm_pipe {
+	void __iomem *tail;
+	void __iomem *head;
+
+	void __iomem *fifo;
+
+	size_t length;
+};
+
+/**
+ * struct glink_defer_cmd - deferred incoming control message
+ * @node:	list node
+ * @msg:	message header
+ * data:	payload of the message
+ *
+ * Copy of a received control message, to be added to @rx_queue and processed
+ * by @rx_work of @glink_rpm.
+ */
+struct glink_defer_cmd {
+	struct list_head node;
+
+	struct glink_msg msg;
+	u8 data[];
+};
+
+/**
+ * struct glink_rpm - driver context, relates to one remote subsystem
+ * @dev:	reference to the associated struct device
+ * @doorbell:	"rpm_hlos" ipc doorbell
+ * @rx_pipe:	pipe object for receive FIFO
+ * @tx_pipe:	pipe object for transmit FIFO
+ * @irq:	IRQ for signaling incoming events
+ * @rx_work:	worker for handling received control messages
+ * @rx_lock:	protects the @rx_queue
+ * @rx_queue:	queue of received control messages to be processed in @rx_work
+ * @tx_lock:	synchronizes operations on the tx fifo
+ * @idr_lock:	synchronizes @lcids and @rcids modifications
+ * @lcids:	idr of all channels with a known local channel id
+ * @rcids:	idr of all channels with a known remote channel id
+ */
+struct glink_rpm {
+	struct device *dev;
+
+	struct mbox_client mbox_client;
+	struct mbox_chan *mbox_chan;
+
+	struct glink_rpm_pipe rx_pipe;
+	struct glink_rpm_pipe tx_pipe;
+
+	int irq;
+
+	struct work_struct rx_work;
+	spinlock_t rx_lock;
+	struct list_head rx_queue;
+
+	struct mutex tx_lock;
+
+	struct mutex idr_lock;
+	struct idr lcids;
+	struct idr rcids;
+};
+
+enum {
+	GLINK_STATE_CLOSED,
+	GLINK_STATE_OPENING,
+	GLINK_STATE_OPEN,
+	GLINK_STATE_CLOSING,
+};
+
+/**
+ * struct glink_channel - internal representation of a channel
+ * @rpdev:	rpdev reference, only used for primary endpoints
+ * @ept:	rpmsg endpoint this channel is associated with
+ * @glink:	glink_rpm context handle
+ * @refcount:	refcount for the channel object
+ * @recv_lock:	guard for @ept.cb
+ * @name:	unique channel name/identifier
+ * @lcid:	channel id, in local space
+ * @rcid:	channel id, in remote space
+ * @buf:	receive buffer, for gathering fragments
+ * @buf_offset:	write offset in @buf
+ * @buf_size:	size of current @buf
+ * @open_ack:	completed once remote has acked the open-request
+ * @open_req:	completed once open-request has been received
+ */
+struct glink_channel {
+	struct rpmsg_endpoint ept;
+
+	struct rpmsg_device *rpdev;
+	struct glink_rpm *glink;
+
+	struct kref refcount;
+
+	spinlock_t recv_lock;
+
+	char *name;
+	unsigned int lcid;
+	unsigned int rcid;
+
+	void *buf;
+	int buf_offset;
+	int buf_size;
+
+	struct completion open_ack;
+	struct completion open_req;
+};
+
+#define to_glink_channel(_ept) container_of(_ept, struct glink_channel, ept)
+
+static const struct rpmsg_endpoint_ops glink_endpoint_ops;
+
+#define RPM_CMD_VERSION			0
+#define RPM_CMD_VERSION_ACK		1
+#define RPM_CMD_OPEN			2
+#define RPM_CMD_CLOSE			3
+#define RPM_CMD_OPEN_ACK		4
+#define RPM_CMD_TX_DATA			9
+#define RPM_CMD_CLOSE_ACK		11
+#define RPM_CMD_TX_DATA_CONT		12
+#define RPM_CMD_READ_NOTIF		13
+
+#define GLINK_FEATURE_INTENTLESS	BIT(1)
+
+static struct glink_channel *glink_rpm_alloc_channel(struct glink_rpm *glink,
+						     const char *name)
+{
+	struct glink_channel *channel;
+
+	channel = kzalloc(sizeof(*channel), GFP_KERNEL);
+	if (!channel)
+		return ERR_PTR(-ENOMEM);
+
+	/* Setup glink internal glink_channel data */
+	spin_lock_init(&channel->recv_lock);
+	channel->glink = glink;
+	channel->name = kstrdup(name, GFP_KERNEL);
+
+	init_completion(&channel->open_req);
+	init_completion(&channel->open_ack);
+
+	kref_init(&channel->refcount);
+
+	return channel;
+}
+
+static void glink_rpm_channel_release(struct kref *ref)
+{
+	struct glink_channel *channel = container_of(ref, struct glink_channel,
+						     refcount);
+
+	kfree(channel->name);
+	kfree(channel);
+}
+
+static size_t glink_rpm_rx_avail(struct glink_rpm *glink)
+{
+	struct glink_rpm_pipe *pipe = &glink->rx_pipe;
+	unsigned int head;
+	unsigned int tail;
+
+	head = readl(pipe->head);
+	tail = readl(pipe->tail);
+
+	if (head < tail)
+		return pipe->length - tail + head;
+	else
+		return head - tail;
+}
+
+static void glink_rpm_rx_peak(struct glink_rpm *glink,
+			      void *data, size_t count)
+{
+	struct glink_rpm_pipe *pipe = &glink->rx_pipe;
+	unsigned int tail;
+	size_t len;
+
+	tail = readl(pipe->tail);
+
+	len = min_t(size_t, count, pipe->length - tail);
+	if (len) {
+		__ioread32_copy(data, pipe->fifo + tail,
+				len / sizeof(u32));
+	}
+
+	if (len != count) {
+		__ioread32_copy(data + len, pipe->fifo,
+				(count - len) / sizeof(u32));
+	}
+}
+
+static void glink_rpm_rx_advance(struct glink_rpm *glink,
+				 size_t count)
+{
+	struct glink_rpm_pipe *pipe = &glink->rx_pipe;
+	unsigned int tail;
+
+	tail = readl(pipe->tail);
+
+	tail += count;
+	if (tail >= pipe->length)
+		tail -= pipe->length;
+
+	writel(tail, pipe->tail);
+}
+
+static size_t glink_rpm_tx_avail(struct glink_rpm *glink)
+{
+	struct glink_rpm_pipe *pipe = &glink->tx_pipe;
+	unsigned int head;
+	unsigned int tail;
+
+	head = readl(pipe->head);
+	tail = readl(pipe->tail);
+
+	if (tail <= head)
+		return pipe->length - head + tail;
+	else
+		return tail - head;
+}
+
+static unsigned int glink_rpm_tx_write(struct glink_rpm *glink,
+				       unsigned int head,
+				       const void *data, size_t count)
+{
+	struct glink_rpm_pipe *pipe = &glink->tx_pipe;
+	size_t len;
+
+	len = min_t(size_t, count, pipe->length - head);
+	if (len) {
+		__iowrite32_copy(pipe->fifo + head, data,
+				 len / sizeof(u32));
+	}
+
+	if (len != count) {
+		__iowrite32_copy(pipe->fifo, data + len,
+				 (count - len) / sizeof(u32));
+	}
+
+	head += count;
+	if (head >= pipe->length)
+		head -= pipe->length;
+
+	return head;
+}
+
+static int glink_rpm_tx(struct glink_rpm *glink,
+			const void *hdr, size_t hlen,
+			const void *data, size_t dlen, bool wait)
+{
+	struct glink_rpm_pipe *pipe = &glink->tx_pipe;
+	unsigned int head;
+	unsigned int tlen = hlen + dlen;
+	int ret;
+
+	/* Reject packets that are too big */
+	if (tlen >= glink->tx_pipe.length)
+		return -EINVAL;
+
+	if (WARN(tlen % 8, "Unaligned TX request"))
+		return -EINVAL;
+
+	ret = mutex_lock_interruptible(&glink->tx_lock);
+	if (ret)
+		return ret;
+
+	while (glink_rpm_tx_avail(glink) < tlen) {
+		if (!wait) {
+			ret = -ENOMEM;
+			goto out;
+		}
+
+		msleep(10);
+	}
+
+	head = readl(pipe->head);
+	head = glink_rpm_tx_write(glink, head, hdr, hlen);
+	head = glink_rpm_tx_write(glink, head, data, dlen);
+	writel(head, pipe->head);
+
+	mbox_send_message(glink->mbox_chan, NULL);
+	mbox_client_txdone(glink->mbox_chan, 0);
+
+out:
+	mutex_unlock(&glink->tx_lock);
+
+	return ret;
+}
+
+static int glink_rpm_send_version(struct glink_rpm *glink)
+{
+	struct glink_msg msg;
+
+	msg.cmd = cpu_to_le16(RPM_CMD_VERSION);
+	msg.param1 = cpu_to_le16(1);
+	msg.param2 = cpu_to_le32(GLINK_FEATURE_INTENTLESS);
+
+	return glink_rpm_tx(glink, &msg, sizeof(msg), NULL, 0, true);
+}
+
+static void glink_rpm_send_version_ack(struct glink_rpm *glink)
+{
+	struct glink_msg msg;
+
+	msg.cmd = cpu_to_le16(RPM_CMD_VERSION_ACK);
+	msg.param1 = cpu_to_le16(1);
+	msg.param2 = cpu_to_le32(0);
+
+	glink_rpm_tx(glink, &msg, sizeof(msg), NULL, 0, true);
+}
+
+static void glink_rpm_send_open_ack(struct glink_rpm *glink,
+					 struct glink_channel *channel)
+{
+	struct glink_msg msg;
+
+	msg.cmd = cpu_to_le16(RPM_CMD_OPEN_ACK);
+	msg.param1 = cpu_to_le16(channel->rcid);
+	msg.param2 = cpu_to_le32(0);
+
+	glink_rpm_tx(glink, &msg, sizeof(msg), NULL, 0, true);
+}
+
+/**
+ * glink_rpm_send_open_req() - send a RPM_CMD_OPEN request to the remote
+ * @glink:
+ * @channel:
+ *
+ * Allocates a local channel id and sends a RPM_CMD_OPEN message to the remote.
+ * Will return with refcount held, regardless of outcome.
+ *
+ * Returns 0 on success, negative errno otherwise.
+ */
+static int glink_rpm_send_open_req(struct glink_rpm *glink,
+					 struct glink_channel *channel)
+{
+	struct {
+		struct glink_msg msg;
+		u8 name[GLINK_NAME_SIZE];
+	} __packed req;
+	int name_len = strlen(channel->name) + 1;
+	int req_len = ALIGN(sizeof(req.msg) + name_len, 8);
+	int ret;
+
+	kref_get(&channel->refcount);
+
+	mutex_lock(&glink->idr_lock);
+	ret = idr_alloc_cyclic(&glink->lcids, channel,
+			       RPM_GLINK_CID_MIN, RPM_GLINK_CID_MAX, GFP_KERNEL);
+	mutex_unlock(&glink->idr_lock);
+	if (ret < 0)
+		return ret;
+
+	channel->lcid = ret;
+
+	req.msg.cmd = cpu_to_le16(RPM_CMD_OPEN);
+	req.msg.param1 = cpu_to_le16(channel->lcid);
+	req.msg.param2 = cpu_to_le32(name_len);
+	strcpy(req.name, channel->name);
+
+	ret = glink_rpm_tx(glink, &req, req_len, NULL, 0, true);
+	if (ret)
+		goto remove_idr;
+
+	return 0;
+
+remove_idr:
+	mutex_lock(&glink->idr_lock);
+	idr_remove(&glink->lcids, channel->lcid);
+	channel->lcid = 0;
+	mutex_unlock(&glink->idr_lock);
+
+	return ret;
+}
+
+static void glink_rpm_send_close_req(struct glink_rpm *glink,
+					  struct glink_channel *channel)
+{
+	struct glink_msg req;
+
+	req.cmd = cpu_to_le16(RPM_CMD_CLOSE);
+	req.param1 = cpu_to_le16(channel->lcid);
+	req.param2 = 0;
+
+	glink_rpm_tx(glink, &req, sizeof(req), NULL, 0, true);
+}
+
+static void glink_rpm_send_close_ack(struct glink_rpm *glink, unsigned int rcid)
+{
+	struct glink_msg req;
+
+	req.cmd = cpu_to_le16(RPM_CMD_CLOSE_ACK);
+	req.param1 = cpu_to_le16(rcid);
+	req.param2 = 0;
+
+	glink_rpm_tx(glink, &req, sizeof(req), NULL, 0, true);
+}
+
+static int glink_rpm_rx_defer(struct glink_rpm *glink, size_t extra)
+{
+	struct glink_defer_cmd *dcmd;
+
+	extra = ALIGN(extra, 8);
+
+	if (glink_rpm_rx_avail(glink) < sizeof(struct glink_msg) + extra) {
+		dev_dbg(glink->dev, "Insufficient data in rx fifo");
+		return -ENXIO;
+	}
+
+	dcmd = kzalloc(sizeof(*dcmd) + extra, GFP_ATOMIC);
+	if (!dcmd)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&dcmd->node);
+
+	glink_rpm_rx_peak(glink, &dcmd->msg, sizeof(dcmd->msg) + extra);
+
+	spin_lock(&glink->rx_lock);
+	list_add_tail(&dcmd->node, &glink->rx_queue);
+	spin_unlock(&glink->rx_lock);
+
+	schedule_work(&glink->rx_work);
+	glink_rpm_rx_advance(glink, sizeof(dcmd->msg) + extra);
+
+	return 0;
+}
+
+static int glink_rpm_rx_data(struct glink_rpm *glink, size_t avail)
+{
+	struct glink_channel *channel;
+	struct {
+		struct glink_msg msg;
+		__le32 chunk_size;
+		__le32 left_size;
+	} __packed hdr;
+	unsigned int chunk_size;
+	unsigned int left_size;
+	unsigned int rcid;
+
+	if (avail < sizeof(hdr)) {
+		dev_dbg(glink->dev, "Not enough data in fifo\n");
+		return -EAGAIN;
+	}
+
+	glink_rpm_rx_peak(glink, &hdr, sizeof(hdr));
+	chunk_size = le32_to_cpu(hdr.chunk_size);
+	left_size = le32_to_cpu(hdr.left_size);
+
+	if (avail < sizeof(hdr) + chunk_size) {
+		dev_dbg(glink->dev, "Payload not yet in fifo\n");
+		return -EAGAIN;
+	}
+
+	if (WARN(chunk_size % 4, "Incoming data must be word aligned\n"))
+		return -EINVAL;
+
+	rcid = le16_to_cpu(hdr.msg.param1);
+	channel = idr_find(&glink->rcids, rcid);
+	if (!channel) {
+		dev_dbg(glink->dev, "Data on non-existing channel\n");
+
+		/* Drop the message */
+		glink_rpm_rx_advance(glink, ALIGN(sizeof(hdr) + chunk_size, 8));
+		return 0;
+	}
+
+	/* Might have an ongoing, fragmented, message to append */
+	if (!channel->buf) {
+		channel->buf = kmalloc(chunk_size + left_size, GFP_ATOMIC);
+		if (!channel->buf)
+			return -ENOMEM;
+
+		channel->buf_size = chunk_size + left_size;
+		channel->buf_offset = 0;
+	}
+
+	glink_rpm_rx_advance(glink, sizeof(hdr));
+
+	if (channel->buf_size - channel->buf_offset < chunk_size) {
+		dev_err(glink->dev, "Insufficient space in input buffer\n");
+
+		/* The packet header lied, drop payload */
+		glink_rpm_rx_advance(glink, chunk_size);
+		return -ENOMEM;
+	}
+
+	glink_rpm_rx_peak(glink, channel->buf + channel->buf_offset, chunk_size);
+	channel->buf_offset += chunk_size;
+
+	/* Handle message when no fragments remain to be received */
+	if (!left_size) {
+		spin_lock(&channel->recv_lock);
+		if (channel->ept.cb) {
+			channel->ept.cb(channel->ept.rpdev,
+					channel->buf,
+					channel->buf_offset,
+					channel->ept.priv,
+					RPMSG_ADDR_ANY);
+		}
+		spin_unlock(&channel->recv_lock);
+
+		kfree(channel->buf);
+		channel->buf = NULL;
+		channel->buf_size = 0;
+	}
+
+	/* Each message starts at 8 byte aligned address */
+	glink_rpm_rx_advance(glink, ALIGN(chunk_size, 8));
+
+	return 0;
+}
+
+static int glink_rpm_rx_open_ack(struct glink_rpm *glink, unsigned int lcid)
+{
+	struct glink_channel *channel;
+
+	channel = idr_find(&glink->lcids, lcid);
+	if (!channel) {
+		dev_err(glink->dev, "Invalid open ack packet\n");
+		return -EINVAL;
+	}
+
+	complete(&channel->open_ack);
+
+	return 0;
+}
+
+static irqreturn_t glink_rpm_intr(int irq, void *data)
+{
+	struct glink_rpm *glink = data;
+	struct glink_msg msg;
+	unsigned int param1;
+	unsigned int param2;
+	unsigned int avail;
+	unsigned int cmd;
+	int ret;
+
+	for (;;) {
+		avail = glink_rpm_rx_avail(glink);
+		if (avail < sizeof(msg))
+			break;
+
+		glink_rpm_rx_peak(glink, &msg, sizeof(msg));
+
+		cmd = le16_to_cpu(msg.cmd);
+		param1 = le16_to_cpu(msg.param1);
+		param2 = le32_to_cpu(msg.param2);
+
+		switch (cmd) {
+		case RPM_CMD_VERSION:
+		case RPM_CMD_VERSION_ACK:
+		case RPM_CMD_CLOSE:
+		case RPM_CMD_CLOSE_ACK:
+			ret = glink_rpm_rx_defer(glink, 0);
+			break;
+		case RPM_CMD_OPEN_ACK:
+			ret = glink_rpm_rx_open_ack(glink, param1);
+			glink_rpm_rx_advance(glink, ALIGN(sizeof(msg), 8));
+			break;
+		case RPM_CMD_OPEN:
+			ret = glink_rpm_rx_defer(glink, param2);
+			break;
+		case RPM_CMD_TX_DATA:
+		case RPM_CMD_TX_DATA_CONT:
+			ret = glink_rpm_rx_data(glink, avail);
+			break;
+		case RPM_CMD_READ_NOTIF:
+			glink_rpm_rx_advance(glink, ALIGN(sizeof(msg), 8));
+
+			mbox_send_message(glink->mbox_chan, NULL);
+			mbox_client_txdone(glink->mbox_chan, 0);
+
+			ret = 0;
+			break;
+		default:
+			dev_err(glink->dev, "unhandled rx cmd: %d\n", cmd);
+			ret = -EINVAL;
+			break;
+		}
+
+		if (ret)
+			break;
+	}
+
+	return IRQ_HANDLED;
+}
+
+/* Locally initiated rpmsg_create_ept */
+static struct glink_channel *glink_rpm_create_local(struct glink_rpm *glink,
+						    const char *name)
+{
+	struct glink_channel *channel;
+	int ret;
+
+	channel = glink_rpm_alloc_channel(glink, name);
+	if (IS_ERR(channel))
+		return ERR_CAST(channel);
+
+	ret = glink_rpm_send_open_req(glink, channel);
+	if (ret)
+		goto release_channel;
+
+	ret = wait_for_completion_timeout(&channel->open_ack, 5 * HZ);
+	if (!ret)
+		goto err_timeout;
+
+	ret = wait_for_completion_timeout(&channel->open_req, 5 * HZ);
+	if (!ret)
+		goto err_timeout;
+
+	glink_rpm_send_open_ack(glink, channel);
+
+	return channel;
+
+err_timeout:
+	/* glink_rpm_send_open_req() did register the channel in lcids*/
+	mutex_lock(&glink->idr_lock);
+	idr_remove(&glink->lcids, channel->lcid);
+	mutex_unlock(&glink->idr_lock);
+
+release_channel:
+	/* Release glink_rpm_send_open_req() reference */
+	kref_put(&channel->refcount, glink_rpm_channel_release);
+	/* Release glink_rpm_alloc_channel() reference */
+	kref_put(&channel->refcount, glink_rpm_channel_release);
+
+	return ERR_PTR(-ETIMEDOUT);
+}
+
+/* Remote initiated rpmsg_create_ept */
+static int glink_rpm_create_remote(struct glink_rpm *glink,
+				   struct glink_channel *channel)
+{
+	int ret;
+
+	glink_rpm_send_open_ack(glink, channel);
+
+	ret = glink_rpm_send_open_req(glink, channel);
+	if (ret)
+		goto close_link;
+
+	ret = wait_for_completion_timeout(&channel->open_ack, 5 * HZ);
+	if (!ret) {
+		ret = -ETIMEDOUT;
+		goto close_link;
+	}
+
+	return 0;
+
+close_link:
+	/*
+	 * Send a close request to "undo" our open-ack. The close-ack will
+	 * release the last reference.
+	 */
+	glink_rpm_send_close_req(glink, channel);
+
+	/* Release glink_rpm_send_open_req() reference */
+	kref_put(&channel->refcount, glink_rpm_channel_release);
+
+	return ret;
+}
+
+static struct rpmsg_endpoint *glink_rpm_create_ept(struct rpmsg_device *rpdev,
+						  rpmsg_rx_cb_t cb, void *priv,
+						  struct rpmsg_channel_info chinfo)
+{
+	struct glink_channel *parent = to_glink_channel(rpdev->ept);
+	struct glink_channel *channel;
+	struct glink_rpm *glink = parent->glink;
+	struct rpmsg_endpoint *ept;
+	const char *name = chinfo.name;
+	int cid;
+	int ret;
+
+	idr_for_each_entry(&glink->rcids, channel, cid) {
+		if (!strcmp(channel->name, name))
+			break;
+	}
+
+	if (!channel) {
+		channel = glink_rpm_create_local(glink, name);
+		if (IS_ERR(channel))
+			return NULL;
+	} else {
+		ret = glink_rpm_create_remote(glink, channel);
+		if (ret)
+			return NULL;
+	}
+
+	ept = &channel->ept;
+	ept->rpdev = rpdev;
+	ept->cb = cb;
+	ept->priv = priv;
+	ept->ops = &glink_endpoint_ops;
+
+	return ept;
+}
+
+static void glink_rpm_destroy_ept(struct rpmsg_endpoint *ept)
+{
+	struct glink_channel *channel = to_glink_channel(ept);
+	struct glink_rpm *glink = channel->glink;
+	unsigned long flags;
+
+	spin_lock_irqsave(&channel->recv_lock, flags);
+	channel->ept.cb = NULL;
+	spin_unlock_irqrestore(&channel->recv_lock, flags);
+
+	/* Decouple the potential rpdev from the channel */
+	channel->rpdev = NULL;
+
+	glink_rpm_send_close_req(glink, channel);
+}
+
+static int __glink_rpm_send(struct glink_channel *channel,
+			     void *data, int len, bool wait)
+{
+	struct glink_rpm *glink = channel->glink;
+	struct {
+		struct glink_msg msg;
+		__le32 chunk_size;
+		__le32 left_size;
+	} __packed req;
+
+	if (WARN(len % 8, "RPM GLINK expects 8 byte aligned messages\n"))
+		return -EINVAL;
+
+	req.msg.cmd = cpu_to_le16(RPM_CMD_TX_DATA);
+	req.msg.param1 = cpu_to_le16(channel->lcid);
+	req.msg.param2 = cpu_to_le32(channel->rcid);
+	req.chunk_size = cpu_to_le32(len);
+	req.left_size = cpu_to_le32(0);
+
+	return glink_rpm_tx(glink, &req, sizeof(req), data, len, wait);
+}
+
+static int glink_rpm_send(struct rpmsg_endpoint *ept, void *data, int len)
+{
+	struct glink_channel *channel = to_glink_channel(ept);
+
+	return __glink_rpm_send(channel, data, len, true);
+}
+
+static int glink_rpm_trysend(struct rpmsg_endpoint *ept, void *data, int len)
+{
+	struct glink_channel *channel = to_glink_channel(ept);
+
+	return __glink_rpm_send(channel, data, len, false);
+}
+
+/*
+ * Finds the device_node for the glink child interested in this channel.
+ */
+static struct device_node *glink_rpm_match_channel(struct device_node *node,
+						    const char *channel)
+{
+	struct device_node *child;
+	const char *name;
+	const char *key;
+	int ret;
+
+	for_each_available_child_of_node(node, child) {
+		key = "qcom,glink-channels";
+		ret = of_property_read_string(child, key, &name);
+		if (ret)
+			continue;
+
+		if (strcmp(name, channel) == 0)
+			return child;
+	}
+
+	return NULL;
+}
+
+static const struct rpmsg_device_ops glink_device_ops = {
+	.create_ept = glink_rpm_create_ept,
+};
+
+static const struct rpmsg_endpoint_ops glink_endpoint_ops = {
+	.destroy_ept = glink_rpm_destroy_ept,
+	.send = glink_rpm_send,
+	.trysend = glink_rpm_trysend,
+};
+
+static void glink_rpm_rpdev_release(struct device *dev)
+{
+	struct rpmsg_device *rpdev = to_rpmsg_device(dev);
+	struct glink_channel *channel = to_glink_channel(rpdev->ept);
+
+	channel->rpdev = NULL;
+	kfree(rpdev);
+}
+
+static int glink_rpm_rx_open(struct glink_rpm *glink, unsigned int rcid,
+			     char *name)
+{
+	struct glink_channel *channel;
+	struct rpmsg_device *rpdev;
+	bool create_device = false;
+	int lcid;
+	int ret;
+
+	idr_for_each_entry(&glink->lcids, channel, lcid) {
+		if (!strcmp(channel->name, name))
+			break;
+	}
+
+	if (!channel) {
+		channel = glink_rpm_alloc_channel(glink, name);
+		if (IS_ERR(channel))
+			return PTR_ERR(channel);
+
+		/* The opening dance was initiated by the remote */
+		create_device = true;
+	}
+
+	mutex_lock(&glink->idr_lock);
+	ret = idr_alloc(&glink->rcids, channel, rcid, rcid + 1, GFP_KERNEL);
+	if (ret < 0) {
+		dev_err(glink->dev, "Unable to insert channel into rcid list\n");
+		mutex_unlock(&glink->idr_lock);
+		goto free_channel;
+	}
+	channel->rcid = ret;
+	mutex_unlock(&glink->idr_lock);
+
+	complete(&channel->open_req);
+
+	if (create_device) {
+		rpdev = kzalloc(sizeof(*rpdev), GFP_KERNEL);
+		if (!rpdev) {
+			ret = -ENOMEM;
+			goto rcid_remove;
+		}
+
+		rpdev->ept = &channel->ept;
+		strncpy(rpdev->id.name, name, RPMSG_NAME_SIZE);
+		rpdev->src = RPMSG_ADDR_ANY;
+		rpdev->dst = RPMSG_ADDR_ANY;
+		rpdev->ops = &glink_device_ops;
+
+		rpdev->dev.of_node = glink_rpm_match_channel(glink->dev->of_node, name);
+		rpdev->dev.parent = glink->dev;
+		rpdev->dev.release = glink_rpm_rpdev_release;
+
+		ret = rpmsg_register_device(rpdev);
+		if (ret)
+			goto free_rpdev;
+
+		channel->rpdev = rpdev;
+	}
+
+	return 0;
+
+free_rpdev:
+	kfree(rpdev);
+rcid_remove:
+	mutex_lock(&glink->idr_lock);
+	idr_remove(&glink->rcids, channel->rcid);
+	channel->rcid = 0;
+	mutex_unlock(&glink->idr_lock);
+free_channel:
+	/* Release the reference, iff we took it */
+	if (create_device)
+		kref_put(&channel->refcount, glink_rpm_channel_release);
+
+	return ret;
+}
+
+static void glink_rpm_rx_close(struct glink_rpm *glink, unsigned int rcid)
+{
+	struct rpmsg_channel_info chinfo;
+	struct glink_channel *channel;
+
+	channel = idr_find(&glink->rcids, rcid);
+	if (WARN(!channel, "close request on unknown channel\n"))
+		return;
+
+	if (channel->rpdev) {
+		strncpy(chinfo.name, channel->name, sizeof(chinfo.name));
+		chinfo.src = RPMSG_ADDR_ANY;
+		chinfo.dst = RPMSG_ADDR_ANY;
+
+		rpmsg_unregister_device(glink->dev, &chinfo);
+	}
+
+	glink_rpm_send_close_ack(glink, channel->rcid);
+
+	mutex_lock(&glink->idr_lock);
+	idr_remove(&glink->rcids, channel->rcid);
+	channel->rcid = 0;
+	mutex_unlock(&glink->idr_lock);
+
+	kref_put(&channel->refcount, glink_rpm_channel_release);
+}
+
+static void glink_rpm_rx_close_ack(struct glink_rpm *glink, unsigned int lcid)
+{
+	struct glink_channel *channel;
+
+	channel = idr_find(&glink->lcids, lcid);
+	if (WARN(!channel, "close ack on unknown channel\n"))
+		return;
+
+	mutex_lock(&glink->idr_lock);
+	idr_remove(&glink->lcids, channel->lcid);
+	channel->lcid = 0;
+	mutex_unlock(&glink->idr_lock);
+
+	kref_put(&channel->refcount, glink_rpm_channel_release);
+}
+
+static void glink_rpm_work(struct work_struct *work)
+{
+	struct glink_rpm *glink = container_of(work, struct glink_rpm, rx_work);
+	struct glink_defer_cmd *dcmd;
+	struct glink_msg *msg;
+	unsigned long flags;
+	unsigned int param1;
+	unsigned int param2;
+	unsigned int cmd;
+
+	for (;;) {
+		spin_lock_irqsave(&glink->rx_lock, flags);
+		if (list_empty(&glink->rx_queue)) {
+			spin_unlock_irqrestore(&glink->rx_lock, flags);
+			break;
+		}
+		dcmd = list_first_entry(&glink->rx_queue, struct glink_defer_cmd, node);
+		list_del(&dcmd->node);
+		spin_unlock_irqrestore(&glink->rx_lock, flags);
+
+		msg = &dcmd->msg;
+		cmd = le16_to_cpu(msg->cmd);
+		param1 = le16_to_cpu(msg->param1);
+		param2 = le32_to_cpu(msg->param2);
+
+		switch (cmd) {
+		case RPM_CMD_VERSION:
+			glink_rpm_send_version_ack(glink);
+			break;
+		case RPM_CMD_VERSION_ACK:
+			break;
+		case RPM_CMD_OPEN:
+			glink_rpm_rx_open(glink, param1, msg->data);
+			break;
+		case RPM_CMD_CLOSE:
+			glink_rpm_rx_close(glink, param1);
+			break;
+		case RPM_CMD_CLOSE_ACK:
+			glink_rpm_rx_close_ack(glink, param1);
+			break;
+		default:
+			WARN(1, "Unknown defer object %d\n", cmd);
+			break;
+		}
+
+		kfree(dcmd);
+	}
+}
+
+static int glink_rpm_parse_toc(struct device *dev,
+			       void __iomem *msg_ram,
+			       size_t msg_ram_size,
+			       struct glink_rpm_pipe *rx,
+			       struct glink_rpm_pipe *tx)
+{
+	struct rpm_toc *toc;
+	int num_entries;
+	unsigned int id;
+	size_t offset;
+	size_t size;
+	void *buf;
+	int i;
+
+	buf = kzalloc(RPM_TOC_SIZE, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	__ioread32_copy(buf, msg_ram + msg_ram_size - RPM_TOC_SIZE,
+			RPM_TOC_SIZE / sizeof(u32));
+
+	toc = buf;
+
+	if (le32_to_cpu(toc->magic) != RPM_TOC_MAGIC) {
+		dev_err(dev, "RPM TOC has invalid magic\n");
+		goto err_inval;
+	}
+
+	num_entries = le32_to_cpu(toc->count);
+	if (num_entries > RPM_TOC_MAX_ENTRIES) {
+		dev_err(dev, "Invalid number of toc entries\n");
+		goto err_inval;
+	}
+
+	for (i = 0; i < num_entries; i++) {
+		id = le32_to_cpu(toc->entries[i].id);
+		offset = le32_to_cpu(toc->entries[i].offset);
+		size = le32_to_cpu(toc->entries[i].size);
+
+		if (offset > msg_ram_size || offset + size > msg_ram_size) {
+			dev_err(dev, "TOC entry with invalid size\n");
+			continue;
+		}
+
+		switch (id) {
+		case RPM_RX_FIFO_ID:
+			rx->length = size;
+
+			rx->tail = msg_ram + offset;
+			rx->head = msg_ram + offset + sizeof(u32);
+			rx->fifo = msg_ram + offset + 2 * sizeof(u32);
+			break;
+		case RPM_TX_FIFO_ID:
+			tx->length = size;
+
+			tx->tail = msg_ram + offset;
+			tx->head = msg_ram + offset + sizeof(u32);
+			tx->fifo = msg_ram + offset + 2 * sizeof(u32);
+			break;
+		}
+	}
+
+	if (!rx->fifo || !tx->fifo) {
+		dev_err(dev, "Unable to find rx and tx descriptors\n");
+		goto err_inval;
+	}
+
+	kfree(buf);
+	return 0;
+
+err_inval:
+	kfree(buf);
+	return -EINVAL;
+}
+
+static int glink_rpm_probe(struct platform_device *pdev)
+{
+	struct glink_rpm *glink;
+	struct device_node *np;
+	void __iomem *msg_ram;
+	size_t msg_ram_size;
+	struct device *dev = &pdev->dev;
+	struct resource r;
+	int irq;
+	int ret;
+
+	glink = devm_kzalloc(dev, sizeof(*glink), GFP_KERNEL);
+	if (!glink)
+		return -ENOMEM;
+
+	glink->dev = dev;
+
+	mutex_init(&glink->tx_lock);
+	spin_lock_init(&glink->rx_lock);
+	INIT_LIST_HEAD(&glink->rx_queue);
+	INIT_WORK(&glink->rx_work, glink_rpm_work);
+
+	mutex_init(&glink->idr_lock);
+	idr_init(&glink->lcids);
+	idr_init(&glink->rcids);
+
+	glink->mbox_client.dev = &pdev->dev;
+	glink->mbox_chan = mbox_request_channel(&glink->mbox_client, 0);
+	if (IS_ERR(glink->mbox_chan)) {
+		if (PTR_ERR(glink->mbox_chan) != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "failed to acquire IPC channel\n");
+		return PTR_ERR(glink->mbox_chan);
+	}
+
+	np = of_parse_phandle(dev->of_node, "qcom,rpm-msg-ram", 0);
+	ret = of_address_to_resource(np, 0, &r);
+	of_node_put(np);
+	if (ret)
+		return ret;
+
+	msg_ram = devm_ioremap(dev, r.start, resource_size(&r));
+	msg_ram_size = resource_size(&r);
+	if (!msg_ram)
+		return -ENOMEM;
+
+	ret = glink_rpm_parse_toc(dev, msg_ram, msg_ram_size,
+				  &glink->rx_pipe, &glink->tx_pipe);
+	if (ret)
+		return ret;
+
+	writel(0, glink->tx_pipe.head);
+	writel(0, glink->rx_pipe.tail);
+
+	irq = platform_get_irq(pdev, 0);
+	ret = devm_request_irq(dev, irq,
+			       glink_rpm_intr,
+			       IRQF_NO_SUSPEND | IRQF_SHARED,
+			       "glink-rpm", glink);
+	if (ret) {
+		dev_err(dev, "Failed to request IRQ\n");
+		return ret;
+	}
+
+	glink->irq = irq;
+
+	ret = glink_rpm_send_version(glink);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, glink);
+
+	return 0;
+}
+
+static int glink_rpm_remove_device(struct device *dev, void *data)
+{
+	device_unregister(dev);
+
+	return 0;
+}
+
+static int glink_rpm_remove(struct platform_device *pdev)
+{
+	struct glink_rpm *glink = platform_get_drvdata(pdev);
+	struct glink_channel *channel;
+	int cid;
+	int ret;
+
+	disable_irq(glink->irq);
+	cancel_work_sync(&glink->rx_work);
+
+	ret = device_for_each_child(glink->dev, NULL, glink_rpm_remove_device);
+	if (ret)
+		dev_warn(glink->dev, "Can't remove GLINK devices: %d\n", ret);
+
+	/* Release any defunct local channels, waiting for close-ack */
+	idr_for_each_entry(&glink->lcids, channel, cid)
+		kref_put(&channel->refcount, glink_rpm_channel_release);
+
+	idr_destroy(&glink->lcids);
+	idr_destroy(&glink->rcids);
+
+	return 0;
+}
+
+static const struct of_device_id glink_rpm_of_match[] = {
+	{ .compatible = "qcom,glink-rpm" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, glink_rpm_of_match);
+
+static struct platform_driver glink_rpm_driver = {
+	.probe = glink_rpm_probe,
+	.remove = glink_rpm_remove,
+	.driver = {
+		.name = "qcom_glink_rpm",
+		.of_match_table = glink_rpm_of_match,
+	},
+};
+
+static int __init glink_rpm_init(void)
+{
+	return platform_driver_register(&glink_rpm_driver);
+}
+subsys_initcall(glink_rpm_init);
+
+static void __exit glink_rpm_exit(void)
+{
+	platform_driver_unregister(&glink_rpm_driver);
+}
+module_exit(glink_rpm_exit);
+
+MODULE_AUTHOR("Bjorn Andersson <bjorn.andersson@linaro.org>");
+MODULE_DESCRIPTION("Qualcomm GLINK RPM driver");
+MODULE_LICENSE("GPL v2");