U5500 : Mailbox logical driver.

The Mailbox is an inter-processor communication device.
Message passing is possible between different CPU's.
The logical driver allows multiplexing of up to 256
logical channels for each physical mailbox.This driver
uses the services of Physical driver in mbox.c

Mailboxes are only supported on U5500.

ST-Ericsson Linux next: 336280
ST-Ericsson ID: AP 274804
ST-Ericsson FOSS-OUT ID: N/00201-FEA 212 8003

Change-Id: I23bf7e76801b69e13e216f34d88ad5371d787683
Signed-off-by: Bibek Basu <bibek.basu@stericsson.com>
Reviewed-on: http://gerrit.lud.stericsson.com/gerrit/20652
Reviewed-by: Srinidhi KASAGAR <srinidhi.kasagar@stericsson.com>

Conflicts:

	arch/arm/mach-ux500/Kconfig
	arch/arm/mach-ux500/Makefile
	drivers/misc/Kconfig
	drivers/misc/Makefile
	drivers/misc/mbox.c

4 files changed, 1714 insertions, 0 deletions

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index a7e16ec23c3..0dc60d236f5 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -512,6 +512,13 @@ config HWMEM
 	  can be used by hardware. It also enables accessing hwmem allocated
 	  memory buffers through a secure id which can be shared across processes.
 
+config U5500_MBOX
+	bool "Mailbox support"
+	depends on (UX500_SOC_DB5500 && U5500_MODEM_IRQ)
+	default y
+	help
+	  Add support for U5500 mailbox communication with modem side
+
 source "drivers/misc/Kconfig.stm"
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index 45a59bb8fce..0b5d16280fc 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -53,3 +53,4 @@ obj-$(CONFIG_U8500_SHRM)        += shrm/
 obj-$(CONFIG_STM_I2S)           += i2s/
 obj-$(CONFIG_STE_AUDIO_IO_DEV)	+= audio_io_dev/
 obj-$(CONFIG_HWMEM)             += hwmem/
+obj-$(CONFIG_U5500_MBOX)	+= mbox.o mbox_channels-db5500.o
diff --git a/drivers/misc/mbox.c b/drivers/misc/mbox.c
new file mode 100644
index 00000000000..2b2d51caf9d
--- /dev/null
+++ b/drivers/misc/mbox.c
@@ -0,0 +1,565 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2010
+ * Author: Stefan Nilsson <stefan.xk.nilsson@stericsson.com> for ST-Ericsson.
+ * Author: Martin Persson <martin.persson@stericsson.com> for ST-Ericsson.
+ * License terms: GNU General Public License (GPL), version 2.
+ */
+
+/*
+ * Mailbox nomenclature:
+ *
+ *       APE           MODEM
+ *           mbox pairX
+ *   ..........................
+ *   .                       .
+ *   .           peer        .
+ *   .     send  ----        .
+ *   .      -->  |  |        .
+ *   .           |  |        .
+ *   .           ----        .
+ *   .                       .
+ *   .           local       .
+ *   .     rec   ----        .
+ *   .           |  | <--    .
+ *   .           |  |        .
+ *   .           ----        .
+ *   .........................
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/interrupt.h>
+#include <linux/spinlock.h>
+#include <linux/errno.h>
+#include <linux/io.h>
+#include <linux/irq.h>
+#include <linux/platform_device.h>
+#include <linux/debugfs.h>
+#include <linux/seq_file.h>
+#include <linux/completion.h>
+#include <mach/mbox-db5500.h>
+
+#define MBOX_NAME "mbox"
+
+#define MBOX_FIFO_DATA        0x000
+#define MBOX_FIFO_ADD         0x004
+#define MBOX_FIFO_REMOVE      0x008
+#define MBOX_FIFO_THRES_FREE  0x00C
+#define MBOX_FIFO_THRES_OCCUP 0x010
+#define MBOX_FIFO_STATUS      0x014
+
+#define MBOX_DISABLE_IRQ 0x4
+#define MBOX_ENABLE_IRQ  0x0
+#define MBOX_LATCH 1
+
+/* Global list of all mailboxes */
+static struct list_head mboxs = LIST_HEAD_INIT(mboxs);
+
+static struct mbox *get_mbox_with_id(u8 id)
+{
+	u8 i;
+	struct list_head *pos = &mboxs;
+	for (i = 0; i <= id; i++)
+		pos = pos->next;
+
+	return (struct mbox *) list_entry(pos, struct mbox, list);
+}
+
+int mbox_send(struct mbox *mbox, u32 mbox_msg, bool block)
+{
+	int res = 0;
+
+	spin_lock(&mbox->lock);
+
+	dev_dbg(&(mbox->pdev->dev),
+		"About to buffer 0x%X to mailbox 0x%X."
+		" ri = %d, wi = %d\n",
+		mbox_msg, (u32)mbox, mbox->read_index,
+		mbox->write_index);
+
+	/* Check if write buffer is full */
+	while (((mbox->write_index + 1) % MBOX_BUF_SIZE) == mbox->read_index) {
+		if (!block) {
+			dev_dbg(&(mbox->pdev->dev),
+			"Buffer full in non-blocking call! "
+			"Returning -ENOMEM!\n");
+			res = -ENOMEM;
+			goto exit;
+		}
+		spin_unlock(&mbox->lock);
+		dev_dbg(&(mbox->pdev->dev),
+			"Buffer full in blocking call! Sleeping...\n");
+		mbox->client_blocked = 1;
+		wait_for_completion(&mbox->buffer_available);
+		dev_dbg(&(mbox->pdev->dev),
+			"Blocking send was woken up! Trying again...\n");
+		spin_lock(&mbox->lock);
+	}
+
+	mbox->buffer[mbox->write_index] = mbox_msg;
+	mbox->write_index = (mbox->write_index + 1) % MBOX_BUF_SIZE;
+
+	/*
+	 * Indicate that we want an IRQ as soon as there is a slot
+	 * in the FIFO
+	 */
+	writel(MBOX_ENABLE_IRQ, mbox->virtbase_peer + MBOX_FIFO_THRES_FREE);
+
+exit:
+	spin_unlock(&mbox->lock);
+	return res;
+}
+EXPORT_SYMBOL(mbox_send);
+
+#if defined(CONFIG_DEBUG_FS)
+/*
+ * Expected input: <value> <nbr sends>
+ * Example: "echo 0xdeadbeef 4 > mbox-node" sends 0xdeadbeef 4 times
+ */
+static ssize_t mbox_write_fifo(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf,
+			       size_t count)
+{
+	unsigned long mbox_mess;
+	unsigned long nbr_sends;
+	unsigned long i;
+	char int_buf[16];
+	char *token;
+	char *val;
+
+	struct mbox *mbox = (struct mbox *) dev->platform_data;
+
+	strncpy((char *) &int_buf, buf, sizeof(int_buf));
+	token = (char *) &int_buf;
+
+	/* Parse message */
+	val = strsep(&token, " ");
+	if ((val == NULL) || (strict_strtoul(val, 16, &mbox_mess) != 0))
+		mbox_mess = 0xDEADBEEF;
+
+	val = strsep(&token, " ");
+	if ((val == NULL) || (strict_strtoul(val, 10, &nbr_sends) != 0))
+		nbr_sends = 1;
+
+	dev_dbg(dev, "Will write 0x%lX %ld times using data struct at 0x%X\n",
+		mbox_mess, nbr_sends, (u32) mbox);
+
+	for (i = 0; i < nbr_sends; i++)
+		mbox_send(mbox, mbox_mess, true);
+
+	return count;
+}
+
+static ssize_t mbox_read_fifo(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	int mbox_value;
+	struct mbox *mbox = (struct mbox *) dev->platform_data;
+
+	if ((readl(mbox->virtbase_local + MBOX_FIFO_STATUS) & 0x7) <= 0)
+		return sprintf(buf, "Mailbox is empty\n");
+
+	mbox_value = readl(mbox->virtbase_local + MBOX_FIFO_DATA);
+	writel(MBOX_LATCH, (mbox->virtbase_local + MBOX_FIFO_REMOVE));
+
+	return sprintf(buf, "0x%X\n", mbox_value);
+}
+
+static DEVICE_ATTR(fifo, S_IWUGO | S_IRUGO, mbox_read_fifo, mbox_write_fifo);
+
+static int mbox_show(struct seq_file *s, void *data)
+{
+	struct list_head *pos;
+	u8 mbox_index = 0;
+
+	list_for_each(pos, &mboxs) {
+		struct mbox *m =
+			(struct mbox *) list_entry(pos, struct mbox, list);
+		if (m == NULL) {
+			seq_printf(s,
+				   "Unable to retrieve mailbox %d\n",
+				   mbox_index);
+			continue;
+		}
+
+		spin_lock(&m->lock);
+		if ((m->virtbase_peer == NULL) || (m->virtbase_local == NULL)) {
+			seq_printf(s, "MAILBOX %d not setup or corrupt\n",
+				   mbox_index);
+			spin_unlock(&m->lock);
+			continue;
+		}
+
+		seq_printf(s,
+		"===========================\n"
+		" MAILBOX %d\n"
+		" PEER MAILBOX DUMP\n"
+		"---------------------------\n"
+		"FIFO:                 0x%X (%d)\n"
+		"Free     Threshold:   0x%.2X (%d)\n"
+		"Occupied Threshold:   0x%.2X (%d)\n"
+		"Status:               0x%.2X (%d)\n"
+		"   Free spaces  (ot):    %d (%d)\n"
+		"   Occup spaces (ot):    %d (%d)\n"
+		"===========================\n"
+		" LOCAL MAILBOX DUMP\n"
+		"---------------------------\n"
+		"FIFO:                 0x%.X (%d)\n"
+		"Free     Threshold:   0x%.2X (%d)\n"
+		"Occupied Threshold:   0x%.2X (%d)\n"
+		"Status:               0x%.2X (%d)\n"
+		"   Free spaces  (ot):    %d (%d)\n"
+		"   Occup spaces (ot):    %d (%d)\n"
+		"===========================\n"
+		"write_index: %d\n"
+		"read_index : %d\n"
+		"===========================\n"
+		"\n",
+		mbox_index,
+		readl(m->virtbase_peer + MBOX_FIFO_DATA),
+		readl(m->virtbase_peer + MBOX_FIFO_DATA),
+		readl(m->virtbase_peer + MBOX_FIFO_THRES_FREE),
+		readl(m->virtbase_peer + MBOX_FIFO_THRES_FREE),
+		readl(m->virtbase_peer + MBOX_FIFO_THRES_OCCUP),
+		readl(m->virtbase_peer + MBOX_FIFO_THRES_OCCUP),
+		readl(m->virtbase_peer + MBOX_FIFO_STATUS),
+		readl(m->virtbase_peer + MBOX_FIFO_STATUS),
+		(readl(m->virtbase_peer + MBOX_FIFO_STATUS) >> 4) & 0x7,
+		(readl(m->virtbase_peer + MBOX_FIFO_STATUS) >> 7) & 0x1,
+		(readl(m->virtbase_peer + MBOX_FIFO_STATUS) >> 0) & 0x7,
+		(readl(m->virtbase_peer + MBOX_FIFO_STATUS) >> 3) & 0x1,
+		readl(m->virtbase_local + MBOX_FIFO_DATA),
+		readl(m->virtbase_local + MBOX_FIFO_DATA),
+		readl(m->virtbase_local + MBOX_FIFO_THRES_FREE),
+		readl(m->virtbase_local + MBOX_FIFO_THRES_FREE),
+		readl(m->virtbase_local + MBOX_FIFO_THRES_OCCUP),
+		readl(m->virtbase_local + MBOX_FIFO_THRES_OCCUP),
+		readl(m->virtbase_local + MBOX_FIFO_STATUS),
+		readl(m->virtbase_local + MBOX_FIFO_STATUS),
+		(readl(m->virtbase_local + MBOX_FIFO_STATUS) >> 4) & 0x7,
+		(readl(m->virtbase_local + MBOX_FIFO_STATUS) >> 7) & 0x1,
+		(readl(m->virtbase_local + MBOX_FIFO_STATUS) >> 0) & 0x7,
+		(readl(m->virtbase_local + MBOX_FIFO_STATUS) >> 3) & 0x1,
+		m->write_index, m->read_index);
+		mbox_index++;
+		spin_unlock(&m->lock);
+	}
+
+	return 0;
+}
+
+static int mbox_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, mbox_show, NULL);
+}
+
+static const struct file_operations mbox_operations = {
+	.owner = THIS_MODULE,
+	.open = mbox_open,
+	.read = seq_read,
+	.llseek = seq_lseek,
+	.release = single_release,
+};
+#endif
+
+static irqreturn_t mbox_irq(int irq, void *arg)
+{
+	u32 mbox_value;
+	int nbr_occup;
+	int nbr_free;
+	struct mbox *mbox = (struct mbox *) arg;
+
+	spin_lock(&mbox->lock);
+
+	dev_dbg(&(mbox->pdev->dev),
+		"mbox IRQ [%d] received. ri = %d, wi = %d\n",
+		irq, mbox->read_index, mbox->write_index);
+
+	/*
+	 * Check if we have any outgoing messages, and if there is space for
+	 * them in the FIFO.
+	 */
+	if (mbox->read_index != mbox->write_index) {
+		/*
+		 * Check by reading FREE for LOCAL since that indicates
+		 * OCCUP for PEER
+		 */
+		nbr_free = (readl(mbox->virtbase_local + MBOX_FIFO_STATUS)
+			    >> 4) & 0x7;
+		dev_dbg(&(mbox->pdev->dev),
+			"Status indicates %d empty spaces in the FIFO!\n",
+			nbr_free);
+
+		while ((nbr_free > 0) &&
+		       (mbox->read_index != mbox->write_index)) {
+			/* Write the message and latch it into the FIFO */
+			writel(mbox->buffer[mbox->read_index],
+			       (mbox->virtbase_peer + MBOX_FIFO_DATA));
+			writel(MBOX_LATCH,
+			       (mbox->virtbase_peer + MBOX_FIFO_ADD));
+			dev_dbg(&(mbox->pdev->dev),
+				"Wrote message 0x%X to addr 0x%X\n",
+				mbox->buffer[mbox->read_index],
+				(u32) (mbox->virtbase_peer + MBOX_FIFO_DATA));
+
+			nbr_free--;
+			mbox->read_index =
+				(mbox->read_index + 1) % MBOX_BUF_SIZE;
+		}
+
+		/*
+		 * Check if we still want IRQ:s when there is free
+		 * space to send
+		 */
+		if (mbox->read_index != mbox->write_index) {
+			dev_dbg(&(mbox->pdev->dev),
+				"Still have messages to send, but FIFO full. "
+				"Request IRQ again!\n");
+			writel(MBOX_ENABLE_IRQ,
+			       mbox->virtbase_peer + MBOX_FIFO_THRES_FREE);
+		} else {
+			dev_dbg(&(mbox->pdev->dev),
+				"No more messages to send. "
+				"Do not request IRQ again!\n");
+			writel(MBOX_DISABLE_IRQ,
+			       mbox->virtbase_peer + MBOX_FIFO_THRES_FREE);
+		}
+
+		/*
+		 * Check if we can signal any blocked clients that it is OK to
+		 * start buffering again
+		 */
+		if (mbox->client_blocked &&
+		    (((mbox->write_index + 1) % MBOX_BUF_SIZE)
+		     != mbox->read_index)) {
+			dev_dbg(&(mbox->pdev->dev),
+				"Waking up blocked client\n");
+			complete(&mbox->buffer_available);
+			mbox->client_blocked = 0;
+		}
+	}
+
+	/* Check if we have any incoming messages */
+	nbr_occup = readl(mbox->virtbase_local + MBOX_FIFO_STATUS) & 0x7;
+	if (nbr_occup == 0)
+		goto exit;
+
+	if (mbox->cb == NULL) {
+		dev_dbg(&(mbox->pdev->dev), "No receive callback registered, "
+			"leaving %d incoming messages in fifo!\n", nbr_occup);
+		goto exit;
+	}
+
+	/* Read and acknowledge the message */
+	mbox_value = readl(mbox->virtbase_local + MBOX_FIFO_DATA);
+	writel(MBOX_LATCH, (mbox->virtbase_local + MBOX_FIFO_REMOVE));
+
+	/* Notify consumer of new mailbox message */
+	dev_dbg(&(mbox->pdev->dev), "Calling callback for message 0x%X!\n",
+		mbox_value);
+	mbox->cb(mbox_value, mbox->client_data);
+
+exit:
+	dev_dbg(&(mbox->pdev->dev), "Exit mbox IRQ. ri = %d, wi = %d\n",
+		mbox->read_index, mbox->write_index);
+	spin_unlock(&mbox->lock);
+
+	return IRQ_HANDLED;
+}
+
+/* Setup is executed once for each mbox pair */
+struct mbox *mbox_setup(u8 mbox_id, mbox_recv_cb_t *mbox_cb, void *priv)
+{
+	struct resource *resource;
+	int irq;
+	int res;
+	struct mbox *mbox;
+
+	mbox = get_mbox_with_id(mbox_id);
+	if (mbox == NULL) {
+		dev_err(&(mbox->pdev->dev), "Incorrect mailbox id: %d!\n",
+			mbox_id);
+		goto exit;
+	}
+
+	/*
+	 * Check if mailbox has been allocated to someone else,
+	 * otherwise allocate it
+	 */
+	if (mbox->allocated) {
+		dev_err(&(mbox->pdev->dev), "Mailbox number %d is busy!\n",
+			mbox_id);
+		mbox = NULL;
+		goto exit;
+	}
+	mbox->allocated = true;
+
+	dev_dbg(&(mbox->pdev->dev), "Initiating mailbox number %d: 0x%X...\n",
+		mbox_id, (u32)mbox);
+
+	mbox->client_data = priv;
+	mbox->cb = mbox_cb;
+
+	/* Get addr for peer mailbox and ioremap it */
+	resource = platform_get_resource_byname(mbox->pdev,
+						IORESOURCE_MEM,
+						"mbox_peer");
+	if (resource == NULL) {
+		dev_err(&(mbox->pdev->dev),
+			"Unable to retrieve mbox peer resource\n");
+		mbox = NULL;
+		goto exit;
+	}
+	dev_dbg(&(mbox->pdev->dev),
+		"Resource name: %s start: 0x%X, end: 0x%X\n",
+		resource->name, resource->start, resource->end);
+	mbox->virtbase_peer = ioremap(resource->start, resource_size(resource));
+	if (!mbox->virtbase_peer) {
+		dev_err(&(mbox->pdev->dev), "Unable to ioremap peer mbox\n");
+		mbox = NULL;
+		goto exit;
+	}
+	dev_dbg(&(mbox->pdev->dev),
+		"ioremapped peer physical: (0x%X-0x%X) to virtual: 0x%X\n",
+		resource->start, resource->end, (u32) mbox->virtbase_peer);
+
+	/* Get addr for local mailbox and ioremap it */
+	resource = platform_get_resource_byname(mbox->pdev,
+						IORESOURCE_MEM,
+						"mbox_local");
+	if (resource == NULL) {
+		dev_err(&(mbox->pdev->dev),
+			"Unable to retrieve mbox local resource\n");
+		mbox = NULL;
+		goto exit;
+	}
+	dev_dbg(&(mbox->pdev->dev),
+		"Resource name: %s start: 0x%X, end: 0x%X\n",
+		resource->name, resource->start, resource->end);
+	mbox->virtbase_local = ioremap(resource->start, resource_size(resource));
+	if (!mbox->virtbase_local) {
+		dev_err(&(mbox->pdev->dev), "Unable to ioremap local mbox\n");
+		mbox = NULL;
+		goto exit;
+	}
+	dev_dbg(&(mbox->pdev->dev),
+		"ioremapped local physical: (0x%X-0x%X) to virtual: 0x%X\n",
+		resource->start, resource->end, (u32) mbox->virtbase_peer);
+
+	init_completion(&mbox->buffer_available);
+	mbox->client_blocked = 0;
+
+	/* Get IRQ for mailbox and allocate it */
+	irq = platform_get_irq_byname(mbox->pdev, "mbox_irq");
+	if (irq < 0) {
+		dev_err(&(mbox->pdev->dev),
+			"Unable to retrieve mbox irq resource\n");
+		mbox = NULL;
+		goto exit;
+	}
+
+	dev_dbg(&(mbox->pdev->dev), "Allocating irq %d...\n", irq);
+	res = request_irq(irq, mbox_irq, 0, mbox->name, (void *) mbox);
+	if (res < 0) {
+		dev_err(&(mbox->pdev->dev),
+			"Unable to allocate mbox irq %d\n", irq);
+		mbox = NULL;
+		goto exit;
+	}
+
+	/* Set up mailbox to not launch IRQ on free space in mailbox */
+	writel(MBOX_DISABLE_IRQ, mbox->virtbase_peer + MBOX_FIFO_THRES_FREE);
+
+	/*
+	 * Set up mailbox to launch IRQ on new message if we have
+	 * a callback set. If not, do not raise IRQ, but keep message
+	 * in FIFO for manual retrieval
+	 */
+	if (mbox_cb != NULL)
+		writel(MBOX_ENABLE_IRQ,
+		       mbox->virtbase_local + MBOX_FIFO_THRES_OCCUP);
+	else
+		writel(MBOX_DISABLE_IRQ,
+		       mbox->virtbase_local + MBOX_FIFO_THRES_OCCUP);
+
+#if defined(CONFIG_DEBUG_FS)
+	res = device_create_file(&(mbox->pdev->dev), &dev_attr_fifo);
+	if (res != 0)
+		dev_warn(&(mbox->pdev->dev),
+			 "Unable to create mbox sysfs entry");
+
+	(void) debugfs_create_file("mbox", S_IFREG | S_IRUGO, NULL,
+				   NULL, &mbox_operations);
+#endif
+
+	dev_info(&(mbox->pdev->dev),
+		 "Mailbox driver with index %d initiated!\n", mbox_id);
+
+exit:
+	return mbox;
+}
+EXPORT_SYMBOL(mbox_setup);
+
+
+int __init mbox_probe(struct platform_device *pdev)
+{
+	struct mbox local_mbox;
+	struct mbox *mbox;
+	int res = 0;
+	dev_dbg(&(pdev->dev), "Probing mailbox (pdev = 0x%X)...\n", (u32) pdev);
+
+	memset(&local_mbox, 0x0, sizeof(struct mbox));
+
+	/* Associate our mbox data with the platform device */
+	res = platform_device_add_data(pdev,
+				       (void *) &local_mbox,
+				       sizeof(struct mbox));
+	if (res != 0) {
+		dev_err(&(pdev->dev),
+			"Unable to allocate driver platform data!\n");
+		goto exit;
+	}
+
+	mbox = (struct mbox *) pdev->dev.platform_data;
+	mbox->pdev = pdev;
+	mbox->write_index = 0;
+	mbox->read_index = 0;
+
+	INIT_LIST_HEAD(&(mbox->list));
+	list_add_tail(&(mbox->list), &mboxs);
+
+	sprintf(mbox->name, "%s", MBOX_NAME);
+	spin_lock_init(&mbox->lock);
+
+	dev_info(&(pdev->dev), "Mailbox driver loaded\n");
+
+exit:
+	return res;
+}
+
+static struct platform_driver mbox_driver = {
+	.driver = {
+		.name = MBOX_NAME,
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init mbox_init(void)
+{
+	return platform_driver_probe(&mbox_driver, mbox_probe);
+}
+
+module_init(mbox_init);
+
+void __exit mbox_exit(void)
+{
+	platform_driver_unregister(&mbox_driver);
+}
+
+module_exit(mbox_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MBOX driver");
diff --git a/drivers/misc/mbox_channels-db5500.c b/drivers/misc/mbox_channels-db5500.c
new file mode 100644
index 00000000000..74fdfa7aaae
--- /dev/null
+++ b/drivers/misc/mbox_channels-db5500.c
@@ -0,0 +1,1141 @@
+/*
+ * Copyright (C) ST-Ericsson SA 2010
+ *
+ * Mailbox Logical Driver
+ *
+ * Author: Marcin Mielczarczyk <marcin.mielczarczyk@tieto.com> for ST-Ericsson.
+ *         Bibek Basu ,bibek.basu@stericsson.com>
+ * License terms: GNU General Public License (GPL), version 2.
+ */
+
+#include <asm/mach-types.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/random.h>
+#include <mach/mbox-db5500.h>
+#include <mach/mbox_channels-db5500.h>
+#include <linux/io.h>
+
+/* Defines start sequence number for given mailbox channel */
+#define CHANNEL_START_SEQUENCE_NUMBER	0x80
+
+/* Defines number of channels per mailbox unit */
+#define CHANNELS_PER_MBOX_UNIT		256
+
+/*
+ * This macro builds mbox channel PDU header with following format:
+ * ---------------------------------------------------------------------------
+ * |                |         |          |                                    |
+ * | Sequence nmbr  |  Type   |  Length  | Destination logical channel number |
+ * |                |         |          |                                    |
+ * ---------------------------------------------------------------------------
+ * 31               24        20         16                    0
+ *
+ */
+#define BUILD_HEADER(chan, len, type, seq_no) \
+			((chan) | (((len) & 0xf) << 16) | \
+			(((type) & 0xf) << 20) | ((seq_no) << 24))
+
+/* Returns type from mbox message header */
+#define GET_TYPE(mbox_msg)			(((mbox_msg) >> 20) & 0xf)
+
+/* Returns channel number from mbox message header */
+#define GET_CHANNEL(mbox_msg)			((mbox_msg) & 0xffff)
+
+/* Returns length of payload from mbox message header */
+#define GET_LENGTH(mbox_msg)			(((mbox_msg) >> 16) & 0xf)
+
+/* Returns sequence number from mbox message header */
+#define GET_SEQ_NUMBER(mbox_msg)		(((mbox_msg) >> 24)
+
+/* Number of buffers */
+#define NUM_DSP_BUFFER	3
+
+/* circular buffer indicator */
+static int buffer_index;
+
+enum mbox_msg{
+	MBOX_CLOSE,
+	MBOX_OPEN,
+	MBOX_SEND,
+	MBOX_CAST,
+	MBOX_ACK,
+	MBOX_NAK,
+};
+
+enum mbox_dir {
+	MBOX_TX,
+	MBOX_RX,
+};
+
+struct mbox_channel_mapping {
+	u16		chan_base;
+	u8		mbox_id;
+	enum mbox_dir	direction;
+};
+
+/* This table maps mbox logical channel to mbox id and direction */
+static struct mbox_channel_mapping channel_mappings[] = {
+	{0x500, 2, MBOX_RX}, /* channel 5 maps to mbox 0.1, dsp->app (unsec) */
+	{0x900, 2, MBOX_TX}, /* channel 9 maps to mbox 0.0, app->dsp (unsec) */
+};
+
+/* This table specifies mailbox ids which mbox channels module will use */
+static u8 mbox_ids[] = {
+	2,		/* app <-> dsp (unsec) */
+};
+
+/**
+ * struct mbox_unit_status - current status of mbox unit
+ * @mbox_id :		holds mbox unit identification number
+ * @mbox :		holds mbox pointer after mbox_register() call
+ * @tx_chans :		holds list of open tx mbox channels
+ * @tx_lock:		lock for tx channel
+ * @rx_chans :		holds list of open rx mbox channels
+ * @rx_lock:		lock for rx channel
+ */
+struct mbox_unit_status {
+	u8			mbox_id;
+	struct mbox		*mbox;
+	struct list_head	tx_chans;
+	spinlock_t		tx_lock;
+	struct list_head	rx_chans;
+	spinlock_t		rx_lock;
+};
+
+static struct {
+	struct platform_device	*pdev;
+	struct mbox_unit_status	mbox_unit[ARRAY_SIZE(mbox_ids)];
+} channels;
+
+/* This structure describes pending element for mbox tx channel */
+struct pending_elem {
+	struct list_head	list;
+	u32			*data;
+	u8			length;
+};
+
+struct rx_pending_elem {
+	u32			buffer[MAILBOX_NR_OF_DATAWORDS];
+	u8			length;
+	void			*priv;
+};
+
+struct rx_pending_elem rx_pending[NUM_DSP_BUFFER + 1];
+
+/* This structure holds list of pending elements for mbox tx channel */
+struct tx_channel {
+	struct list_head	pending;
+};
+
+/* Specific status for mbox rx channel */
+struct rx_channel {
+	struct list_head	pending;
+	spinlock_t		lock;
+	u32			buffer[MAILBOX_NR_OF_DATAWORDS];
+	u8			index;
+	u8			length;
+};
+
+/* This structure holds status of mbox channel - common for tx and rx */
+struct channel_status {
+	struct list_head	list;
+	u16			channel;
+	int			state;
+	mbox_channel_cb_t	*cb;
+	void			*priv;
+	u8			seq_number;
+	bool			with_ack;
+	struct rx_channel	rx;
+	struct tx_channel	tx;
+	struct work_struct	receive_msg;
+	struct work_struct	open_msg;
+	struct work_struct	cast_msg;
+	struct mutex		lock;
+};
+
+/* Checks if provided channel number is valid */
+static bool check_channel(u16 channel, enum mbox_dir direction)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(channel_mappings); i++) {
+		if ((channel >= channel_mappings[i].chan_base) &&
+		    (channel < channel_mappings[i].chan_base +
+		    CHANNELS_PER_MBOX_UNIT)) {
+			/* Check if direction of given channel is correct*/
+			if (channel_mappings[i].direction == direction)
+				return true;
+			else
+				break;
+		}
+	}
+	return false;
+}
+
+/* get the tx channel corresponding to the given rx channel */
+static u16 get_tx_channel(u16 channel)
+{
+	int i;
+	int relative_chan = 0;
+	int mbox_id = 0xFF;
+	u16 tx_channel = 0xFF;
+
+	for (i = 0; i < ARRAY_SIZE(channel_mappings); i++) {
+		if ((channel >= channel_mappings[i].chan_base) &&
+				(channel < channel_mappings[i].chan_base +
+				 CHANNELS_PER_MBOX_UNIT)) {
+			/* Check if direction of given channel is correct*/
+			relative_chan = channel - channel_mappings[i].chan_base;
+			mbox_id = channel_mappings[i].mbox_id;
+
+		}
+	}
+
+	for (i = 0; i < ARRAY_SIZE(channel_mappings); i++) {
+		if ((mbox_id == channel_mappings[i].mbox_id) &&
+				(channel_mappings[i].direction == MBOX_TX))
+			tx_channel = channel_mappings[i].chan_base +
+				relative_chan;
+	}
+	return tx_channel;
+}
+
+/* Returns mbox unit id for given mbox channel */
+static int get_mbox_id(u16 channel)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(channel_mappings); i++) {
+		if ((channel >= channel_mappings[i].chan_base) &&
+		    (channel < channel_mappings[i].chan_base +
+		    CHANNELS_PER_MBOX_UNIT)) {
+			return channel_mappings[i].mbox_id;
+		}
+	}
+	/* There is no mbox unit registered for given channel */
+	return -EINVAL;
+}
+
+/* Returns mbox structure saved after mbox_register() call */
+static struct mbox *get_mbox(u16 channel)
+{
+	int i;
+	int mbox_id = get_mbox_id(channel);
+
+	if (mbox_id < 0) {
+		dev_err(&channels.pdev->dev, "couldn't get mbox id\n");
+		return NULL;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(channels.mbox_unit); i++) {
+		if (channels.mbox_unit[i].mbox_id == mbox_id)
+			return channels.mbox_unit[i].mbox;
+	}
+	return NULL;
+}
+
+/* Returns pointer to rx mbox channels list for given mbox unit */
+static struct list_head *get_rx_list(u8 mbox_id)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mbox_ids); i++) {
+		if (channels.mbox_unit[i].mbox_id == mbox_id)
+			return &channels.mbox_unit[i].rx_chans;
+	}
+	return NULL;
+}
+
+/* Returns pointer to tx mbox channels list for given mbox unit */
+static struct list_head *get_tx_list(u8 mbox_id)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(mbox_ids); i++) {
+		if (channels.mbox_unit[i].mbox_id == mbox_id)
+			return &channels.mbox_unit[i].tx_chans;
+	}
+	return NULL;
+}
+
+static int send_pdu(struct channel_status *chan_status, int command,
+		u16 channel)
+{
+	struct mbox *mbox;
+	u32 header = 0;
+	int ret = 0;
+
+	/* SEND PDU is not supported */
+	if (command == MBOX_SEND) {
+		dev_err(&channels.pdev->dev, "SEND command not implemented\n");
+		ret = -EINVAL;
+		goto exit;
+	}
+	mbox = get_mbox(chan_status->channel);
+	if (mbox == NULL) {
+		dev_err(&channels.pdev->dev, "couldn't get mailbox\n");
+		ret = -ENOSYS;
+		goto exit;
+	}
+	/* For CAST type send all pending messages */
+	if (command == MBOX_CAST) {
+		struct list_head *pos, *n;
+
+		/* Send all pending messages from TX channel */
+		list_for_each_safe(pos, n, &chan_status->tx.pending) {
+			struct pending_elem *pending =
+				list_entry(pos, struct pending_elem, list);
+			int i;
+
+			header = BUILD_HEADER(channel,
+					pending->length,
+					command,
+					chan_status->seq_number);
+
+			ret = mbox_send(mbox, header, true);
+			if (ret < 0) {
+				dev_err(&channels.pdev->dev,
+					"failed to send header, err=%d\n", ret);
+				goto exit;
+			}
+
+			for (i = 0; i < pending->length; i++) {
+				ret = mbox_send(mbox, pending->data[i], true);
+				if (ret < 0) {
+					dev_err(&channels.pdev->dev,
+					"failed to send header, err=%d\n", ret);
+					goto exit;
+				}
+			}
+
+			/* Call client's callback that data is already sent */
+			if (chan_status->cb)
+				chan_status->cb(pending->data, pending->length,
+						chan_status->priv);
+			else
+				dev_err(&channels.pdev->dev,
+					"%s no callback provided\n", __func__);
+
+			/* Increment sequence number */
+			chan_status->seq_number++;
+
+			/* Remove and free element from the list */
+			list_del(&pending->list);
+			kfree(pending);
+		}
+	} else {
+		header = BUILD_HEADER(channel, 0,
+				command, chan_status->seq_number);
+
+		ret = mbox_send(mbox, header, true);
+		if (ret < 0)
+			dev_err(&channels.pdev->dev, "failed to send header\n");
+		/* Increment sequence number */
+		chan_status->seq_number++;
+	}
+
+exit:
+	return ret;
+}
+
+void mbox_handle_receive_msg(struct work_struct *work)
+{
+	struct channel_status *rx_chan = container_of(work,
+			struct channel_status,
+			receive_msg);
+
+	/* Call client's callback and reset state */
+	if (rx_chan->cb) {
+		static int rx_pending_count;
+
+		if (rx_pending_count == NUM_DSP_BUFFER)
+			rx_pending_count = 0;
+		else
+			rx_pending_count++;
+	rx_chan->cb(rx_pending[rx_pending_count].buffer,
+			rx_pending[rx_pending_count].length,
+			rx_pending[rx_pending_count].priv);
+		buffer_index--;
+	} else {
+		dev_err(&channels.pdev->dev,
+				"%s no callback provided\n", __func__);
+	}
+
+}
+
+void mbox_handle_open_msg(struct work_struct *work)
+{
+	struct channel_status *tx_chan = container_of(work,
+							struct channel_status,
+							 open_msg);
+	/* Change channel state to OPEN */
+	tx_chan->state = MBOX_OPEN;
+	/* If pending list not empty, start sending data */
+	if (!list_empty(&tx_chan->tx.pending))
+		send_pdu(tx_chan, MBOX_CAST, tx_chan->channel);
+}
+
+void mbox_handle_cast_msg(struct work_struct *work)
+{
+	struct channel_status *rx_chan = container_of(work,
+							struct channel_status,
+							 cast_msg);
+	/* Check if channel is opened */
+	if (rx_chan->state == MBOX_CLOSE) {
+		/* Peer sent message to closed channel */
+		dev_err(&channels.pdev->dev,
+			"channel in wrong state\n");
+	}
+}
+
+static bool handle_receive_msg(u32 mbox_msg, struct list_head *rx_list)
+{
+	struct list_head *pos;
+	struct channel_status *tmp;
+	int i;
+	static int rx_pending_count;
+	struct channel_status *rx_chan = NULL;
+	struct mbox_unit_status *mbox_unit = container_of(rx_list,
+			struct mbox_unit_status,
+			rx_chans);
+	spin_lock(&mbox_unit->rx_lock);
+	list_for_each(pos, rx_list) {
+		tmp = list_entry(pos, struct channel_status, list);
+		if (tmp->state == MBOX_SEND ||
+				tmp->state == MBOX_CAST)
+			/* Received message is payload */
+			rx_chan = tmp;
+	}
+	/* Received message is header */
+	spin_unlock(&mbox_unit->rx_lock);
+	if (rx_chan) {
+		/* Store received data in RX channel buffer */
+		rx_chan->rx.buffer[rx_chan->rx.index++] = mbox_msg;
+		/* Check if it's last data of PDU */
+		if (rx_chan->rx.index == rx_chan->rx.length) {
+			if (rx_pending_count == NUM_DSP_BUFFER)
+				rx_pending_count = 0;
+			else
+				rx_pending_count++;
+			for (i = 0; i < MAILBOX_NR_OF_DATAWORDS; i++) {
+				rx_pending[rx_pending_count].buffer[i] =
+					rx_chan->rx.buffer[i];
+			}
+			rx_pending[rx_pending_count].length =
+				rx_chan->rx.length;
+			rx_pending[rx_pending_count].priv = rx_chan->priv;
+			rx_chan->rx.index = 0;
+			rx_chan->rx.length = 0;
+			rx_chan->state = MBOX_OPEN;
+			rx_chan->seq_number++;
+			buffer_index++;
+			if (buffer_index >= NUM_DSP_BUFFER)
+				dev_err(&channels.pdev->dev,
+					"rxbuf overflow%d\n", buffer_index);
+			schedule_work(&rx_chan->receive_msg);
+		}
+		dev_dbg(&channels.pdev->dev, "%s OK\n", __func__);
+		return true;
+	}
+	return false;
+}
+
+static void handle_open_msg(u16 channel, u8 mbox_id)
+{
+	struct list_head *tx_list, *pos;
+	struct channel_status *tmp;
+	struct channel_status *tx_chan = NULL;
+	struct mbox_unit_status *mbox_unit;
+	channel = get_tx_channel(channel);
+	dev_dbg(&channels.pdev->dev, "%s mbox_id %d\tchannel %x\n",
+			__func__, mbox_id, channel);
+	/* Get TX channesenx for given mbox unit */
+	tx_list = get_tx_list(mbox_id);
+	if (tx_list == NULL) {
+		dev_err(&channels.pdev->dev, "given mbox id is not valid %d\n",
+			mbox_id);
+		return;
+	}
+	mbox_unit = container_of(tx_list, struct mbox_unit_status, tx_chans);
+	/* Search for channel in tx list */
+	spin_lock(&mbox_unit->tx_lock);
+	list_for_each(pos, tx_list) {
+		tmp = list_entry(pos, struct channel_status, list);
+		dev_dbg(&channels.pdev->dev, "tmp->channel=%d\n",
+				tmp->channel);
+		if (tmp->channel == channel)
+			tx_chan = tmp;
+	}
+	spin_unlock(&mbox_unit->tx_lock);
+	if (tx_chan) {
+		schedule_work(&tx_chan->open_msg);
+	} else {
+		/* No tx channel found on the list, allocate new element */
+		tx_chan = kzalloc(sizeof(*tx_chan), GFP_KERNEL);
+		if (tx_chan == NULL) {
+			dev_err(&channels.pdev->dev,
+				"failed to allocate memory\n");
+			return;
+		}
+
+		/* Fill initial data and add this element to tx list */
+		tx_chan->channel = get_tx_channel(channel);
+		tx_chan->state = MBOX_OPEN;
+		tx_chan->seq_number = CHANNEL_START_SEQUENCE_NUMBER;
+		INIT_LIST_HEAD(&tx_chan->tx.pending);
+		INIT_WORK(&tx_chan->open_msg, mbox_handle_open_msg);
+		INIT_WORK(&tx_chan->cast_msg, mbox_handle_cast_msg);
+		INIT_WORK(&tx_chan->receive_msg, mbox_handle_receive_msg);
+		mutex_init(&tx_chan->lock);
+		spin_lock(&mbox_unit->tx_lock);
+		list_add_tail(&tx_chan->list, tx_list);
+		spin_unlock(&mbox_unit->tx_lock);
+	}
+}
+
+static void handle_cast_msg(u16 channel, struct list_head *rx_list,
+						u32 mbox_msg, bool send)
+{
+	struct list_head *pos;
+	struct channel_status *tmp;
+	struct channel_status *rx_chan = NULL;
+	struct mbox_unit_status *mbox_unit = container_of(rx_list,
+						struct mbox_unit_status,
+							 rx_chans);
+	dev_dbg(&channels.pdev->dev, " %s\n", __func__);
+	/* Search for channel in rx list */
+	spin_lock(&mbox_unit->rx_lock);
+	list_for_each(pos, rx_list) {
+		tmp = list_entry(pos, struct channel_status, list);
+		if (tmp->channel == channel)
+			rx_chan = tmp;
+	}
+	spin_unlock(&mbox_unit->rx_lock);
+
+	if (rx_chan) {
+		rx_chan->rx.buffer[0] = mbox_msg;
+		rx_chan->with_ack = send;
+		rx_chan->rx.length = GET_LENGTH(rx_chan->rx.buffer[0]);
+		if (rx_chan->rx.length <= MAILBOX_NR_OF_DATAWORDS &&
+				rx_chan->rx.length > 0) {
+			rx_chan->rx.index = 0;
+			rx_chan->state = MBOX_CAST;
+		}
+		schedule_work(&rx_chan->cast_msg);
+	} else {
+		/* Channel not found, peer sent wrong message */
+		dev_err(&channels.pdev->dev, "channel %d doesn't exist\n",
+			channel);
+	}
+}
+
+/*
+ * This callback is called whenever mbox unit receives data.
+ * priv parameter holds mbox unit id.
+ */
+static void mbox_cb(u32 mbox_msg, void *priv)
+{
+	u8 mbox_id = *(u8 *)priv;
+	struct list_head *rx_list;
+	u8 type = GET_TYPE(mbox_msg);
+	u16 channel = GET_CHANNEL(mbox_msg);
+
+	dev_dbg(&channels.pdev->dev, "%s type %d\t, mbox_msg %x\n",
+		       __func__, type, mbox_msg);
+	/* Get RX channels list for given mbox unit */
+	rx_list = get_rx_list(mbox_id);
+	if (rx_list == NULL) {
+		dev_err(&channels.pdev->dev, "given mbox id is not valid %d\n",
+				mbox_id);
+		return;
+	}
+
+	/* If received message is payload this function will take care of it */
+	if (handle_receive_msg(mbox_msg, rx_list))
+		return;
+
+	/* Received message is header as no RX channel is in SEND/CAST state */
+	switch (type) {
+	case MBOX_CLOSE:
+		/* Not implemented */
+		break;
+	case MBOX_OPEN:
+		handle_open_msg(channel, mbox_id);
+		break;
+	case MBOX_SEND:
+		handle_cast_msg(channel, rx_list, mbox_msg, true);
+		break;
+	case MBOX_CAST:
+		handle_cast_msg(channel, rx_list, mbox_msg, false);
+		break;
+	case MBOX_ACK:
+	case MBOX_NAK:
+		/* Not implemented */
+		break;
+	}
+}
+
+int mbox_channel_register(u16 channel, mbox_channel_cb_t *cb, void *priv)
+{
+	struct channel_status *rx_chan;
+	struct list_head *pos, *rx_list;
+	int res = 0;
+	struct mbox_unit_status *mbox_unit;
+
+	dev_dbg(&channels.pdev->dev, " %s channel = %d\n", __func__, channel);
+	/* Closing of channels is not implemented */
+	if (cb == NULL) {
+		dev_err(&channels.pdev->dev,
+			"channel close is not implemented\n");
+		res = -EINVAL;
+		goto exit;
+	}
+
+	/* Check if provided channel number is valid */
+	if (!check_channel(channel, MBOX_RX)) {
+		dev_err(&channels.pdev->dev, "wrong mbox channel number %d\n",
+			channel);
+		res = -EINVAL;
+		goto exit;
+	}
+
+	rx_list = get_rx_list(get_mbox_id(channel));
+	if (rx_list == NULL) {
+		dev_err(&channels.pdev->dev, "given mbox id is not valid\n");
+		res = -EINVAL;
+		goto exit;
+	}
+
+	mbox_unit = container_of(rx_list, struct mbox_unit_status, rx_chans);
+
+	/* Check if channel is already registered */
+	spin_lock(&mbox_unit->rx_lock);
+	list_for_each(pos, rx_list) {
+		rx_chan = list_entry(pos, struct channel_status, list);
+
+		if (rx_chan->channel == channel) {
+			dev_dbg(&channels.pdev->dev,
+				"channel already registered\n");
+			rx_chan->cb = cb;
+			rx_chan->priv = priv;
+			spin_unlock(&mbox_unit->rx_lock);
+			goto exit;
+		}
+	}
+	spin_unlock(&mbox_unit->rx_lock);
+
+	rx_chan = kzalloc(sizeof(*rx_chan), GFP_KERNEL);
+	if (rx_chan == NULL) {
+		dev_err(&channels.pdev->dev,
+			"couldn't allocate channel status\n");
+		res = -ENOMEM;
+		goto exit;
+	}
+
+	/* Fill out newly allocated element and add it to rx list */
+	rx_chan->channel = channel;
+	rx_chan->cb = cb;
+	rx_chan->priv = priv;
+	rx_chan->seq_number = CHANNEL_START_SEQUENCE_NUMBER;
+	mutex_init(&rx_chan->lock);
+	INIT_LIST_HEAD(&rx_chan->rx.pending);
+	INIT_WORK(&rx_chan->open_msg, mbox_handle_open_msg);
+	INIT_WORK(&rx_chan->cast_msg, mbox_handle_cast_msg);
+	INIT_WORK(&rx_chan->receive_msg, mbox_handle_receive_msg);
+	spin_lock(&mbox_unit->rx_lock);
+	list_add_tail(&rx_chan->list, rx_list);
+	spin_unlock(&mbox_unit->rx_lock);
+
+	mutex_lock(&rx_chan->lock);
+	res = send_pdu(rx_chan, MBOX_OPEN, get_tx_channel(rx_chan->channel));
+	if (res) {
+		dev_err(&channels.pdev->dev, "failed to send OPEN command\n");
+		spin_lock(&mbox_unit->rx_lock);
+		list_del(&rx_chan->list);
+		spin_unlock(&mbox_unit->rx_lock);
+		kfree(rx_chan);
+	} else {
+		rx_chan->seq_number++;
+		rx_chan->state = MBOX_OPEN;
+	}
+	mutex_unlock(&rx_chan->lock);
+exit:
+	return res;
+}
+EXPORT_SYMBOL(mbox_channel_register);
+
+int mbox_channel_send(struct mbox_channel_msg *msg)
+{
+	struct list_head *pos, *tx_list;
+	struct channel_status *tmp = NULL;
+	struct channel_status *tx_chan = NULL;
+	struct pending_elem *pending;
+	struct mbox_unit_status *mbox_unit;
+
+	if (msg->length > MAILBOX_NR_OF_DATAWORDS || msg->length == 0) {
+		dev_err(&channels.pdev->dev, "data length incorrect\n");
+		return -EINVAL;
+	}
+
+	if (!check_channel(msg->channel, MBOX_TX)) {
+		dev_err(&channels.pdev->dev, "wrong channel number %d\n",
+			msg->channel);
+		return -EINVAL;
+	}
+
+	tx_list = get_tx_list(get_mbox_id(msg->channel));
+	if (tx_list == NULL) {
+		dev_err(&channels.pdev->dev, "given mbox id is not valid\n");
+		return -EINVAL;
+	}
+
+	mbox_unit = container_of(tx_list, struct mbox_unit_status, tx_chans);
+
+	spin_lock(&mbox_unit->tx_lock);
+	dev_dbg(&channels.pdev->dev, "send:tx_list=%x\tmbox_unit=%x\n",
+			(u32)tx_list, (u32)mbox_unit);
+	list_for_each(pos, tx_list) {
+		tmp = list_entry(pos, struct channel_status, list);
+		if (tmp->channel == msg->channel)
+			tx_chan = tmp;
+	}
+	spin_unlock(&mbox_unit->tx_lock);
+	/* Allocate pending element and add it to the list */
+	pending = kzalloc(sizeof(*pending), GFP_KERNEL);
+	if (pending == NULL) {
+		dev_err(&channels.pdev->dev,
+			"couldn't allocate memory for pending\n");
+		return -ENOMEM;
+	}
+	pending->data = msg->data;
+	pending->length = msg->length;
+
+	if (tx_chan) {
+		mutex_lock(&tx_chan->lock);
+		list_add_tail(&pending->list, &tx_chan->tx.pending);
+		tx_chan->cb = msg->cb;
+		tx_chan->priv = msg->priv;
+		/* If channel is already opened start sending data */
+		if (tx_chan->state == MBOX_OPEN)
+			send_pdu(tx_chan, MBOX_CAST, tx_chan->channel);
+		/* Stop processing here */
+		mutex_unlock(&tx_chan->lock);
+	} else {
+		/* No channel found on the list, allocate new element */
+		tx_chan = kzalloc(sizeof(*tx_chan), GFP_KERNEL);
+		if (tx_chan == NULL) {
+			dev_err(&channels.pdev->dev,
+					"couldn't allocate memory for \
+					tx_chan\n");
+			return -ENOMEM;
+		}
+		tx_chan->channel = msg->channel;
+		tx_chan->cb = msg->cb;
+		tx_chan->priv = msg->priv;
+		tx_chan->state = MBOX_CLOSE;
+		tx_chan->seq_number = CHANNEL_START_SEQUENCE_NUMBER;
+		INIT_LIST_HEAD(&tx_chan->tx.pending);
+		INIT_WORK(&tx_chan->open_msg, mbox_handle_open_msg);
+		INIT_WORK(&tx_chan->cast_msg, mbox_handle_cast_msg);
+		INIT_WORK(&tx_chan->receive_msg, mbox_handle_receive_msg);
+		mutex_init(&tx_chan->lock);
+		spin_lock(&mbox_unit->tx_lock);
+		list_add_tail(&tx_chan->list, tx_list);
+		spin_unlock(&mbox_unit->tx_lock);
+		mutex_lock(&tx_chan->lock);
+		list_add_tail(&pending->list, &tx_chan->tx.pending);
+		mutex_unlock(&tx_chan->lock);
+	}
+	return 0;
+}
+EXPORT_SYMBOL(mbox_channel_send);
+
+static void revoke_pending_msgs(struct channel_status *tx_chan)
+{
+	struct list_head *pos, *n;
+	struct pending_elem *pending;
+
+	list_for_each_safe(pos, n, &tx_chan->tx.pending) {
+		pending = list_entry(pos, struct pending_elem, list);
+
+		if (tx_chan->cb)
+			tx_chan->cb(pending->data, pending->length,
+							tx_chan->priv);
+		else
+			dev_err(&channels.pdev->dev,
+				"%s no callback provided\n", __func__);
+		list_del(&pending->list);
+		kfree(pending);
+	}
+}
+
+/* Clear all pending messages from TX channel */
+int mbox_channel_revoke_messages(u16 channel)
+{
+	struct list_head *pos, *tx_list;
+	struct channel_status *tmp;
+	struct channel_status *tx_chan = NULL;
+	struct mbox_unit_status *mbox_unit;
+	int res = 0;
+
+	if (!check_channel(channel, MBOX_TX)) {
+		dev_err(&channels.pdev->dev,
+			"wrong channel number %d\n", channel);
+		return -EINVAL;
+	}
+
+	tx_list = get_tx_list(get_mbox_id(channel));
+	if (tx_list == NULL) {
+		dev_err(&channels.pdev->dev, "given mbox id is not valid\n");
+		return -EINVAL;
+	}
+
+	mbox_unit = container_of(tx_list, struct mbox_unit_status, tx_chans);
+
+	spin_lock(&mbox_unit->tx_lock);
+	list_for_each(pos, tx_list) {
+		tmp = list_entry(pos, struct channel_status, list);
+		if (tmp->channel == channel)
+			tx_chan = tmp;
+	}
+	spin_unlock(&mbox_unit->tx_lock);
+
+	if (tx_chan) {
+		mutex_lock(&tx_chan->lock);
+		revoke_pending_msgs(tx_chan);
+		mutex_unlock(&tx_chan->lock);
+		dev_dbg(&channels.pdev->dev, "channel %d cleared\n",
+			channel);
+	} else {
+		dev_err(&channels.pdev->dev, "no channel found\n");
+		res = -EINVAL;
+	}
+
+	dev_dbg(&channels.pdev->dev, "%s exiting %d\n", __func__, res);
+	return res;
+}
+EXPORT_SYMBOL(mbox_channel_revoke_messages);
+
+#if defined(CONFIG_DEBUG_FS)
+#define MBOXTEST_DEBUG 1
+#ifdef MBOXTEST_DEBUG
+#define DBG_TEST(x)  x
+#else
+#define DBG_TEST(x)
+#endif
+
+#define MBOX_TEST_MAX_WORDS	3
+#define MBOX_RX_CHAN		0x500
+#define MBOX_TX_RX_CHANNEL_DIFF 0x400
+#define MBOX_MAX_NUM_TRANSFER	30000
+static int registration_done;
+/**
+ * struct mboxtest_data - mbox test via debugfs information
+ * @rx_buff:		Buffer for incomming data
+ * @rx_pointer:		Ptr to actual RX data buff
+ * @tx_buff		Buffer for outgoing data
+ * @tx_pointer:		Ptr to actual TX data buff
+ * @tx_done:		TX Transfer done indicator
+ * @rx_done:		RX Transfer done indicator
+ * @received		Received words
+ * @xfer_words:		Num of bytes in actual trf
+ * @xfers:		Number of transfers
+ * @words		Number of total words
+ * @channel:		Channel test number
+ */
+struct mboxtest_data {
+	unsigned int		*rx_buff;
+	unsigned int		*rx_pointer;
+	unsigned int		*tx_buff;
+	unsigned int		*tx_pointer;
+	struct completion	tx_done;
+	struct completion	rx_done;
+	int			received;
+	int			xfer_words;
+	int			xfers;
+	int			words;
+	int			channel;
+};
+
+static void mboxtest_receive_cb(u32 *data, u32 len, void *arg)
+{
+	struct mboxtest_data *mboxtest = (struct mboxtest_data *) arg;
+	int i;
+
+	printk(KERN_INFO "receive_cb.. data.= 0x%X, len = %d\n",
+								*data, len);
+
+	for (i = 0; i < len; i++)
+		*(mboxtest->rx_pointer++) = *(data++);
+
+	mboxtest->received += len;
+
+	printk(KERN_INFO "received = %d, words = %d\n",
+				mboxtest->received, mboxtest->words);
+	if (mboxtest->received >= mboxtest->words)
+		complete(&mboxtest->rx_done);
+	dev_dbg(&channels.pdev->dev, "%s exiting\n", __func__);
+}
+
+static void mboxtest_send_cb(u32 *data, u32 len, void *arg)
+{
+	struct mboxtest_data *mboxtest = (struct mboxtest_data *) arg;
+
+	printk(KERN_INFO "send_cb.. data.= 0x%X, len = %d\n",
+							*data, len);
+
+	complete(&mboxtest->tx_done);
+	dev_dbg(&channels.pdev->dev, "kernel:mboxtest_send_cb exiting\n");
+}
+
+static int mboxtest_transmit(struct mboxtest_data *mboxtest)
+{
+	int status = 0;
+	struct mbox_channel_msg msg;
+
+	dev_dbg(&channels.pdev->dev, "%s entering\n", __func__);
+	init_completion(&mboxtest->tx_done);
+
+	msg.channel = mboxtest->channel;
+	msg.data = mboxtest->tx_pointer;
+	msg.length = mboxtest->words;
+	msg.cb = mboxtest_send_cb;
+	msg.priv = mboxtest;
+
+	status = mbox_channel_send(&msg);
+	if (!status) {
+		mboxtest->tx_pointer += mboxtest->xfer_words;
+		wait_for_completion(&mboxtest->tx_done);
+	}
+
+	dev_dbg(&channels.pdev->dev, "%s exiting %d\n",
+			__func__, status);
+	return status;
+}
+
+static int transfer_test(struct mboxtest_data *mboxtest)
+{
+	int status = 0;
+	int len = 0;
+	int i;
+
+	len = mboxtest->words;
+
+	dev_dbg(&channels.pdev->dev, "%s enterring\n", __func__);
+	/* Allocate buffers */
+	mboxtest->rx_buff = kzalloc(sizeof(unsigned int) * len, GFP_KERNEL);
+	if (!mboxtest->rx_buff) {
+		DBG_TEST(printk(KERN_INFO
+			"Cannot allocate mbox rx memory\n"));
+		status = -ENOMEM;
+		goto err1;
+	}
+	memset(mboxtest->rx_buff, '\0', sizeof(unsigned int) * len);
+
+	mboxtest->tx_buff = kzalloc(sizeof(unsigned int) * len, GFP_KERNEL);
+	if (!mboxtest->tx_buff) {
+		DBG_TEST(printk(KERN_INFO
+			"Cannot allocate mbox tx memory\n"));
+		status = -ENOMEM;
+		goto err2;
+	}
+	memset(mboxtest->tx_buff, '\0', sizeof(unsigned int) * len);
+
+	/* Generate data */
+		get_random_bytes((unsigned char *)mboxtest->tx_buff,
+				sizeof(unsigned int) * len);
+	/* Set pointers */
+	mboxtest->tx_pointer = mboxtest->tx_buff;
+	mboxtest->rx_pointer = mboxtest->rx_buff;
+	mboxtest->received = 0;
+	init_completion(&mboxtest->rx_done);
+
+	/* Start tx transfer test transfer */
+	status = mboxtest_transmit(mboxtest);
+	DBG_TEST(printk(KERN_INFO "xfer_words=%d\n",
+				mboxtest->xfer_words));
+	if (!status)
+		wait_for_completion(&mboxtest->rx_done);
+	for (i = 0; i < len; i++)
+		DBG_TEST(printk(KERN_INFO "%d -> TX:0x%X, RX:0x%X\n", i,
+			mboxtest->tx_buff[i], mboxtest->rx_buff[i]));
+
+	dev_dbg(&channels.pdev->dev, "%s exiting %d\n", __func__, status);
+	return status;
+err2:
+	kfree(mboxtest->rx_buff);
+err1:
+	return status;
+}
+
+static int mboxtest_prepare(struct mboxtest_data *mboxtest)
+{
+	int err = 0;
+
+	mboxtest->xfers = MBOX_MAX_NUM_TRANSFER;
+	/* Calculate number of bytes in each transfer */
+	mboxtest->xfer_words = mboxtest->words / mboxtest->xfers;
+
+	/* Trim to maxiumum data words per transfer */
+	if (mboxtest->xfer_words > MBOX_TEST_MAX_WORDS) {
+		DBG_TEST(printk(KERN_INFO "Recalculating xfers ...\n"));
+		mboxtest->xfer_words = MBOX_TEST_MAX_WORDS;
+		if (mboxtest->words % mboxtest->xfer_words)
+			mboxtest->xfers = (mboxtest->words /
+						mboxtest->xfer_words) + 1;
+		else
+			mboxtest->xfers = (mboxtest->words /
+						mboxtest->xfer_words);
+	}
+
+	DBG_TEST(printk(KERN_INFO "Params: chan=0x%X words=%d, xfers=%d\n",
+			mboxtest->channel, mboxtest->words,
+						mboxtest->xfers));
+
+	if (mbox_channel_register(mboxtest->channel,
+			mboxtest_receive_cb, mboxtest)) {
+		DBG_TEST(printk(KERN_INFO "Cannot register mbox channel\n"));
+		err = -ENOMEM;
+		goto err;
+	}
+
+	registration_done = true;
+	return 0;
+err:
+	kfree(mboxtest);
+	return err;
+}
+
+struct mboxtest_data mboxtest;
+/*
+ * Expected input: <nbr_channel> <nbr_word>
+ * Example: "echo 500 2"
+ */
+static ssize_t mbox_write_channel(struct device *dev,
+			       struct device_attribute *attr,
+			       const char *buf,
+			       size_t count)
+{
+	unsigned long nbr_channel;
+	unsigned long nbr_word;
+	char int_buf[16];
+	char *token;
+	char *val;
+
+	strncpy((char *) &int_buf, buf, sizeof(int_buf));
+	token = (char *) &int_buf;
+
+	/* Parse message */
+	val = strsep(&token, " ");
+	if ((val == NULL) || (strict_strtoul(val, 16, &nbr_channel) != 0))
+		nbr_channel = MBOX_RX_CHAN;
+
+	val = strsep(&token, " ");
+	if ((val == NULL) || (strict_strtoul(val, 16, &nbr_word) != 0))
+		nbr_word = 2;
+
+	dev_dbg(dev, "Will setup logical channel %ld\n", nbr_channel);
+	mboxtest.channel = nbr_channel;
+	mboxtest.words = nbr_word;
+
+	if (!registration_done)
+		mboxtest_prepare(&mboxtest);
+	else
+		dev_dbg(&channels.pdev->dev, "already registration done\n");
+
+	return count;
+}
+
+static ssize_t mbox_read_channel(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+
+	unsigned long i;
+	static bool config_done;
+
+	if (!config_done) {
+		config_done = true;
+		mboxtest.channel += MBOX_TX_RX_CHANNEL_DIFF;
+	}
+	dev_dbg(dev, "Will transfer %d words %d times at channel 0x%x\n",
+			mboxtest.words, mboxtest.xfers, mboxtest.channel);
+	for (i = 0; i < mboxtest.xfers; i++)
+		transfer_test(&mboxtest);
+
+	return 1;
+}
+static DEVICE_ATTR(channel, S_IWUGO | S_IRUGO, mbox_read_channel,
+		mbox_write_channel);
+
+#endif
+
+static int __init mbox_channel_probe(struct platform_device *pdev)
+{
+	int i, ret = 0;
+	struct mbox *mbox;
+
+	dev_dbg(&(pdev->dev), "Probing mailbox (pdev = 0x%X)...\n", (u32)pdev);
+
+	/* Register to given mailbox units (ids) */
+	for (i = 0; i < ARRAY_SIZE(mbox_ids); i++) {
+		mbox = mbox_setup(mbox_ids[i], mbox_cb, &mbox_ids[i]);
+		if (mbox == NULL) {
+			dev_err(&(pdev->dev), "Unable to setup mailbox %d\n",
+				mbox_ids[i]);
+			ret = -EBUSY;
+			goto exit;
+		}
+		channels.mbox_unit[i].mbox_id = mbox_ids[i];
+		channels.mbox_unit[i].mbox = mbox;
+		INIT_LIST_HEAD(&channels.mbox_unit[i].rx_chans);
+		INIT_LIST_HEAD(&channels.mbox_unit[i].tx_chans);
+		spin_lock_init(&channels.mbox_unit[i].rx_lock);
+		spin_lock_init(&channels.mbox_unit[i].tx_lock);
+	}
+
+	channels.pdev = pdev;
+
+	dev_dbg(&(pdev->dev), "Mailbox channel driver loaded\n");
+#if defined(CONFIG_DEBUG_FS)
+	ret = device_create_file(&(pdev->dev), &dev_attr_channel);
+	if (ret != 0)
+		dev_warn(&(pdev->dev),
+			 "Unable to create mbox_channel sysfs entry");
+
+
+#endif
+exit:
+	return ret;
+}
+
+static struct platform_driver mbox_channel_driver = {
+	.driver = {
+		.name = "mbox_channel",
+		.owner = THIS_MODULE,
+	},
+};
+
+static int __init mbox_channel_init(void)
+{
+	if (!machine_is_u5500())
+		return 0;
+
+	platform_device_register_simple("mbox_channel", 0, NULL, 0);
+
+	return platform_driver_probe(&mbox_channel_driver, mbox_channel_probe);
+}
+module_init(mbox_channel_init);
+
+static void __exit mbox_channel_exit(void)
+{
+	platform_driver_unregister(&mbox_channel_driver);
+}
+module_exit(mbox_channel_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MBOX channels driver");