diff mbox

[RFC,v2,2/5] spmi: Linux driver framework for SPMI

Message ID 46db5901fe4d04d09cee8fd81ea1c62068ee9503.1377202730.git.joshc@codeaurora.org (mailing list archive)
State RFC
Headers show

Commit Message

Josh Cartwright Aug. 9, 2013, 8:37 p.m. UTC
From: Kenneth Heitke <kheitke@codeaurora.org>

System Power Management Interface (SPMI) is a specification
developed by the MIPI (Mobile Industry Process Interface) Alliance
optimized for the real time control of Power Management ICs (PMIC).

SPMI is a two-wire serial interface that supports up to 4 master
devices and up to 16 logical slaves.

The framework supports message APIs, multiple busses (1 controller
per bus) and multiple clients/slave devices per controller.

Signed-off-by: Kenneth Heitke <kheitke@codeaurora.org>
Signed-off-by: Michael Bohan <mbohan@codeaurora.org>
Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
---
 drivers/Kconfig                 |   2 +
 drivers/Makefile                |   1 +
 drivers/spmi/Kconfig            |   9 +
 drivers/spmi/Makefile           |   4 +
 drivers/spmi/spmi-dbgfs.c       | 580 ++++++++++++++++++++++++++++++++++++++++
 drivers/spmi/spmi-dbgfs.h       |  25 ++
 drivers/spmi/spmi.c             | 491 ++++++++++++++++++++++++++++++++++
 include/linux/mod_devicetable.h |   8 +
 include/linux/spmi.h            | 355 ++++++++++++++++++++++++
 9 files changed, 1475 insertions(+)
 create mode 100644 drivers/spmi/Kconfig
 create mode 100644 drivers/spmi/Makefile
 create mode 100644 drivers/spmi/spmi-dbgfs.c
 create mode 100644 drivers/spmi/spmi-dbgfs.h
 create mode 100644 drivers/spmi/spmi.c
 create mode 100644 include/linux/spmi.h

Comments

Greg Kroah-Hartman Aug. 22, 2013, 11:10 p.m. UTC | #1
On Fri, Aug 09, 2013 at 01:37:09PM -0700, Josh Cartwright wrote:
> +static char dbgfs_help[] =
> +	"SPMI Debug-FS support\n"
> +	"\n"
> +	"Hierarchy schema:\n"
> +	"/sys/kernel/debug/spmi\n"
> +	"       /help                -- Static help text\n"
> +	"       /spmi-0              -- Directory for SPMI bus 0\n"
> +	"       /spmi-0/0-1          -- Directory for SPMI device '0-1'\n"
> +	"       /spmi-0/0-1/address  -- Starting register for reads or writes\n"
> +	"       /spmi-0/0-1/count    -- Number of registers to read (only used for reads)\n"
> +	"       /spmi-0/0-1/data     -- Initiates the SPMI read (formatted output)\n"
> +	"       /spmi-0/0-1/data_raw -- Initiates the SPMI raw read or write\n"
> +	"       /spmi-n              -- Directory for SPMI bus n\n"
> +	"\n"
> +	"To perform SPMI read or write transactions, you need to first write the\n"
> +	"address of the slave device register to the 'address' file.  For read\n"
> +	"transactions, the number of bytes to be read needs to be written to the\n"
> +	"'count' file.\n"
> +	"\n"
> +	"The 'address' file specifies the 20-bit address of a slave device register.\n"
> +	"The upper 4 bits 'address[19..16]' specify the slave identifier (SID) for\n"
> +	"the slave device.  The lower 16 bits specify the slave register address.\n"
> +	"\n"
> +	"Reading from the 'data' file will initiate a SPMI read transaction starting\n"
> +	"from slave register 'address' for 'count' number of bytes.\n"
> +	"\n"
> +	"Writing to the 'data' file will initiate a SPMI write transaction starting\n"
> +	"from slave register 'address'.  The number of registers written to will\n"
> +	"match the number of bytes written to the 'data' file.\n"
> +	"\n"
> +	"Example: Read 4 bytes starting at register address 0x1234 for SID 2\n"
> +	"\n"
> +	"echo 0x21234 > address\n"
> +	"echo 4 > count\n"
> +	"cat data\n"
> +	"\n"
> +	"Example: Write 3 bytes starting at register address 0x1008 for SID 1\n"
> +	"\n"
> +	"echo 0x11008 > address\n"
> +	"echo 0x01 0x02 0x03 > data\n"
> +	"\n"
> +	"Note that the count file is not used for writes.  Since 3 bytes are\n"
> +	"written to the 'data' file, then 3 bytes will be written across the\n"
> +	"SPMI bus.\n\n";

The help file within the kernel is a nice touch :)

I do know the only rule for debugfs is "There are no rules", but this
looks like you are going to have the way to interact to this bus and
devices as debugfs, is that correct?

Or is this only for "debugging"?  If so, please document it as such.

> +void spmi_dfs_controller_add(struct spmi_controller *ctrl)
> +{
> +	ctrl->dfs_dir = debugfs_create_dir(dev_name(&ctrl->dev),
> +					   spmi_debug_root);
> +	WARN_ON(!ctrl->dfs_dir);

Why?  What is a user going to be able to do with something like this?
You do this in a number of places, please provide "valid" error messages
instead of just kernel stack tracebacks, failing to show the device for
which the error occured (hint, use dev_err()).

Again, never use WARN_ON() as error handling, it's lazy, and wrong.

thanks,

greg k-h
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Josh Cartwright Aug. 23, 2013, 4:06 p.m. UTC | #2
On Thu, Aug 22, 2013 at 04:10:54PM -0700, Greg Kroah-Hartman wrote:
> On Fri, Aug 09, 2013 at 01:37:09PM -0700, Josh Cartwright wrote:
> > +static char dbgfs_help[] =
> > +	"SPMI Debug-FS support\n"
> > +	"\n"
> > +	"Hierarchy schema:\n"
> > +	"/sys/kernel/debug/spmi\n"
> > +	"       /help                -- Static help text\n"
> > +	"       /spmi-0              -- Directory for SPMI bus 0\n"
> > +	"       /spmi-0/0-1          -- Directory for SPMI device '0-1'\n"
> > +	"       /spmi-0/0-1/address  -- Starting register for reads or writes\n"
> > +	"       /spmi-0/0-1/count    -- Number of registers to read (only used for reads)\n"
> > +	"       /spmi-0/0-1/data     -- Initiates the SPMI read (formatted output)\n"
> > +	"       /spmi-0/0-1/data_raw -- Initiates the SPMI raw read or write\n"
> > +	"       /spmi-n              -- Directory for SPMI bus n\n"
> > +	"\n"
> > +	"To perform SPMI read or write transactions, you need to first write the\n"
> > +	"address of the slave device register to the 'address' file.  For read\n"
> > +	"transactions, the number of bytes to be read needs to be written to the\n"
> > +	"'count' file.\n"
> > +	"\n"
> > +	"The 'address' file specifies the 20-bit address of a slave device register.\n"
> > +	"The upper 4 bits 'address[19..16]' specify the slave identifier (SID) for\n"
> > +	"the slave device.  The lower 16 bits specify the slave register address.\n"
> > +	"\n"
> > +	"Reading from the 'data' file will initiate a SPMI read transaction starting\n"
> > +	"from slave register 'address' for 'count' number of bytes.\n"
> > +	"\n"
> > +	"Writing to the 'data' file will initiate a SPMI write transaction starting\n"
> > +	"from slave register 'address'.  The number of registers written to will\n"
> > +	"match the number of bytes written to the 'data' file.\n"
> > +	"\n"
> > +	"Example: Read 4 bytes starting at register address 0x1234 for SID 2\n"
> > +	"\n"
> > +	"echo 0x21234 > address\n"
> > +	"echo 4 > count\n"
> > +	"cat data\n"
> > +	"\n"
> > +	"Example: Write 3 bytes starting at register address 0x1008 for SID 1\n"
> > +	"\n"
> > +	"echo 0x11008 > address\n"
> > +	"echo 0x01 0x02 0x03 > data\n"
> > +	"\n"
> > +	"Note that the count file is not used for writes.  Since 3 bytes are\n"
> > +	"written to the 'data' file, then 3 bytes will be written across the\n"
> > +	"SPMI bus.\n\n";
> 
> The help file within the kernel is a nice touch :)
> 
> I do know the only rule for debugfs is "There are no rules", but this
> looks like you are going to have the way to interact to this bus and
> devices as debugfs, is that correct?

Using debugfs is _a_ way to interact with the controller/slaves, however
it is not _the_ way to do so.  The primary interface is the in-kernel
spmi_{read,write,...}_* functions called within the context of a proper
slave driver.

> Or is this only for "debugging"?  If so, please document it as such.

It's there because it provides a useful interface for debugging of the
controller code, and for simple peek/poke of the slave registers without
having a full driver in place.  Will document this.

> > +void spmi_dfs_controller_add(struct spmi_controller *ctrl)
> > +{
> > +	ctrl->dfs_dir = debugfs_create_dir(dev_name(&ctrl->dev),
> > +					   spmi_debug_root);
> > +	WARN_ON(!ctrl->dfs_dir);
> 
> Why?  What is a user going to be able to do with something like this?
> You do this in a number of places, please provide "valid" error messages
> instead of just kernel stack tracebacks, failing to show the device for
> which the error occured (hint, use dev_err()).

Will do.  Thanks.

> Again, never use WARN_ON() as error handling, it's lazy, and wrong.

To be fair to the original author of this code, this was one of the
'cleanups' I implemented.  So, I'll take full responsibility for the
laziness. :)
Mark Brown Sept. 9, 2013, 3:52 p.m. UTC | #3
On Fri, Aug 23, 2013 at 11:06:25AM -0500, Josh Cartwright wrote:
> On Thu, Aug 22, 2013 at 04:10:54PM -0700, Greg Kroah-Hartman wrote:
> > On Fri, Aug 09, 2013 at 01:37:09PM -0700, Josh Cartwright wrote:

> > > +	"Example: Read 4 bytes starting at register address 0x1234 for SID 2\n"
> > > +	"\n"
> > > +	"echo 0x21234 > address\n"
> > > +	"echo 4 > count\n"
> > > +	"cat data\n"
> > > +	"\n"
> > > +	"Example: Write 3 bytes starting at register address 0x1008 for SID 1\n"
> > > +	"\n"
> > > +	"echo 0x11008 > address\n"
> > > +	"echo 0x01 0x02 0x03 > data\n"
> > > +	"\n"
> > > +	"Note that the count file is not used for writes.  Since 3 bytes are\n"
> > > +	"written to the 'data' file, then 3 bytes will be written across the\n"
> > > +	"SPMI bus.\n\n";

> > The help file within the kernel is a nice touch :)

> > Or is this only for "debugging"?  If so, please document it as such.

> It's there because it provides a useful interface for debugging of the
> controller code, and for simple peek/poke of the slave registers without
> having a full driver in place.  Will document this.

This looks awfully like a version of the debugfs interfaces that regmap
provides, and indeed the entire bus sounds like something that could
idiomatically be supported via regmap.  Have you considered doing that?
This would give access to standard tracepoints as well, plus the cache
infrastructure.
Josh Cartwright Sept. 9, 2013, 4:56 p.m. UTC | #4
Hey Mark-

Thanks for the comments.

On Mon, Sep 09, 2013 at 04:52:24PM +0100, Mark Brown wrote:
> On Fri, Aug 23, 2013 at 11:06:25AM -0500, Josh Cartwright wrote:
> > On Thu, Aug 22, 2013 at 04:10:54PM -0700, Greg Kroah-Hartman wrote:
> > > On Fri, Aug 09, 2013 at 01:37:09PM -0700, Josh Cartwright wrote:
> 
> > > > +	"Example: Read 4 bytes starting at register address 0x1234 for SID 2\n"
> > > > +	"\n"
> > > > +	"echo 0x21234 > address\n"
> > > > +	"echo 4 > count\n"
> > > > +	"cat data\n"
> > > > +	"\n"
> > > > +	"Example: Write 3 bytes starting at register address 0x1008 for SID 1\n"
> > > > +	"\n"
> > > > +	"echo 0x11008 > address\n"
> > > > +	"echo 0x01 0x02 0x03 > data\n"
> > > > +	"\n"
> > > > +	"Note that the count file is not used for writes.  Since 3 bytes are\n"
> > > > +	"written to the 'data' file, then 3 bytes will be written across the\n"
> > > > +	"SPMI bus.\n\n";
> 
> > > The help file within the kernel is a nice touch :)
> 
> > > Or is this only for "debugging"?  If so, please document it as such.
> 
> > It's there because it provides a useful interface for debugging of the
> > controller code, and for simple peek/poke of the slave registers without
> > having a full driver in place.  Will document this.
> 
> This looks awfully like a version of the debugfs interfaces that regmap
> provides, and indeed the entire bus sounds like something that could
> idiomatically be supported via regmap.  Have you considered doing that?
> This would give access to standard tracepoints as well, plus the cache
> infrastructure.

It does indeed look like regmap might work out nicely for SPMI.  I
hadn't seriously considered it just due to a lack of familiarity. I'll
give it a shot and see if I run into any problems.

Thanks,
  Josh
diff mbox

Patch

diff --git a/drivers/Kconfig b/drivers/Kconfig
index aa43b91..2b35420 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -52,6 +52,8 @@  source "drivers/i2c/Kconfig"
 
 source "drivers/spi/Kconfig"
 
+source "drivers/spmi/Kconfig"
+
 source "drivers/hsi/Kconfig"
 
 source "drivers/pps/Kconfig"
diff --git a/drivers/Makefile b/drivers/Makefile
index ab93de8..5c250df 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -64,6 +64,7 @@  obj-$(CONFIG_ATA)		+= ata/
 obj-$(CONFIG_TARGET_CORE)	+= target/
 obj-$(CONFIG_MTD)		+= mtd/
 obj-$(CONFIG_SPI)		+= spi/
+obj-$(CONFIG_SPMI)		+= spmi/
 obj-y				+= hsi/
 obj-y				+= net/
 obj-$(CONFIG_ATM)		+= atm/
diff --git a/drivers/spmi/Kconfig b/drivers/spmi/Kconfig
new file mode 100644
index 0000000..a03835f
--- /dev/null
+++ b/drivers/spmi/Kconfig
@@ -0,0 +1,9 @@ 
+#
+# SPMI driver configuration
+#
+menuconfig SPMI
+	bool "SPMI support"
+	help
+	  SPMI (System Power Management Interface) is a two-wire
+	  serial interface between baseband and application processors
+	  and Power Management Integrated Circuits (PMIC).
diff --git a/drivers/spmi/Makefile b/drivers/spmi/Makefile
new file mode 100644
index 0000000..9d78ec9
--- /dev/null
+++ b/drivers/spmi/Makefile
@@ -0,0 +1,4 @@ 
+#
+# Makefile for kernel SPMI framework.
+#
+obj-$(CONFIG_SPMI)	+= spmi.o spmi-dbgfs.o
diff --git a/drivers/spmi/spmi-dbgfs.c b/drivers/spmi/spmi-dbgfs.c
new file mode 100644
index 0000000..8b6f0e3
--- /dev/null
+++ b/drivers/spmi/spmi-dbgfs.c
@@ -0,0 +1,580 @@ 
+/* Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
+ *
+ * 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/kernel.h>
+#include <linux/module.h>
+#include <linux/sizes.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/spinlock.h>
+#include <linux/string.h>
+#include <linux/debugfs.h>
+#include <linux/spmi.h>
+#include <linux/ctype.h>
+#include "spmi-dbgfs.h"
+
+#define ADDR_LEN	 6	/* 5 byte address + 1 space character */
+#define CHARS_PER_ITEM	 3	/* Format is 'XX ' */
+#define ITEMS_PER_LINE	16	/* 16 data items per line */
+#define MAX_LINE_LENGTH	(ADDR_LEN + (ITEMS_PER_LINE * CHARS_PER_ITEM) + 1)
+
+#define MAX_REG_PER_TRANSACTION	(8)
+
+static const mode_t DFS_MODE = S_IRUSR | S_IWUSR;
+
+/* Log buffer */
+struct spmi_log_buffer {
+	u32 rpos;	/* Current 'read' position in buffer */
+	u32 wpos;	/* Current 'write' position in buffer */
+	u32 len;	/* Length of the buffer */
+	char data[0];	/* Log buffer */
+};
+
+/* SPMI transaction parameters */
+struct spmi_trans {
+	u32 cnt;	/* Number of bytes to read */
+	u32 addr;	/* 20-bit address: SID + PID + Register offset */
+	u32 offset;	/* Offset of last read data */
+	bool raw_data;	/* Set to true for raw data dump */
+	struct spmi_device *sdev;
+	struct spmi_log_buffer *log; /* log buffer */
+};
+
+static char dbgfs_help[] =
+	"SPMI Debug-FS support\n"
+	"\n"
+	"Hierarchy schema:\n"
+	"/sys/kernel/debug/spmi\n"
+	"       /help                -- Static help text\n"
+	"       /spmi-0              -- Directory for SPMI bus 0\n"
+	"       /spmi-0/0-1          -- Directory for SPMI device '0-1'\n"
+	"       /spmi-0/0-1/address  -- Starting register for reads or writes\n"
+	"       /spmi-0/0-1/count    -- Number of registers to read (only used for reads)\n"
+	"       /spmi-0/0-1/data     -- Initiates the SPMI read (formatted output)\n"
+	"       /spmi-0/0-1/data_raw -- Initiates the SPMI raw read or write\n"
+	"       /spmi-n              -- Directory for SPMI bus n\n"
+	"\n"
+	"To perform SPMI read or write transactions, you need to first write the\n"
+	"address of the slave device register to the 'address' file.  For read\n"
+	"transactions, the number of bytes to be read needs to be written to the\n"
+	"'count' file.\n"
+	"\n"
+	"The 'address' file specifies the 20-bit address of a slave device register.\n"
+	"The upper 4 bits 'address[19..16]' specify the slave identifier (SID) for\n"
+	"the slave device.  The lower 16 bits specify the slave register address.\n"
+	"\n"
+	"Reading from the 'data' file will initiate a SPMI read transaction starting\n"
+	"from slave register 'address' for 'count' number of bytes.\n"
+	"\n"
+	"Writing to the 'data' file will initiate a SPMI write transaction starting\n"
+	"from slave register 'address'.  The number of registers written to will\n"
+	"match the number of bytes written to the 'data' file.\n"
+	"\n"
+	"Example: Read 4 bytes starting at register address 0x1234 for SID 2\n"
+	"\n"
+	"echo 0x21234 > address\n"
+	"echo 4 > count\n"
+	"cat data\n"
+	"\n"
+	"Example: Write 3 bytes starting at register address 0x1008 for SID 1\n"
+	"\n"
+	"echo 0x11008 > address\n"
+	"echo 0x01 0x02 0x03 > data\n"
+	"\n"
+	"Note that the count file is not used for writes.  Since 3 bytes are\n"
+	"written to the 'data' file, then 3 bytes will be written across the\n"
+	"SPMI bus.\n\n";
+
+static struct debugfs_blob_wrapper spmi_debug_help = {
+	.data	= dbgfs_help,
+	.size	= sizeof(dbgfs_help),
+};
+
+static struct dentry *spmi_debug_root;
+
+static int spmi_device_dfs_open(struct spmi_device *sdev, struct file *file)
+{
+	struct spmi_log_buffer *log;
+	struct spmi_trans *trans;
+
+	size_t logbufsize = SZ_4K;
+
+	/* Per file "transaction" data */
+	trans = kzalloc(sizeof(*trans), GFP_KERNEL);
+	if (!trans)
+		return -ENOMEM;
+
+	log = kzalloc(logbufsize, GFP_KERNEL);
+	if (!log) {
+		kfree(trans);
+		return -ENOMEM;
+	}
+
+	log->rpos = 0;
+	log->wpos = 0;
+	log->len = logbufsize - sizeof(*log);
+
+	trans->log = log;
+	trans->cnt = sdev->dfs_cnt;
+	trans->addr = sdev->dfs_addr;
+	trans->sdev = sdev;
+	trans->offset = trans->addr;
+
+	file->private_data = trans;
+	return 0;
+}
+
+static int spmi_device_dfs_data_open(struct inode *inode, struct file *file)
+{
+	struct spmi_device *sdev = inode->i_private;
+	return spmi_device_dfs_open(sdev, file);
+}
+
+static int spmi_device_dfs_raw_data_open(struct inode *inode, struct file *file)
+{
+	struct spmi_device *sdev = inode->i_private;
+	struct spmi_trans *trans;
+	int rc;
+
+	rc = spmi_device_dfs_open(sdev, file);
+	trans = file->private_data;
+	trans->raw_data = true;
+	return rc;
+}
+
+static int spmi_device_dfs_close(struct inode *inode, struct file *file)
+{
+	struct spmi_trans *trans = file->private_data;
+	kfree(trans->log);
+	kfree(trans);
+	return 0;
+}
+
+/**
+ * spmi_read_data: reads data across the SPMI bus
+ * @ctrl: The SPMI controller
+ * @buf: buffer to store the data read.
+ * @offset: SPMI address offset to start reading from.
+ * @cnt: The number of bytes to read.
+ *
+ * Returns 0 on success, otherwise returns error code from SPMI driver.
+ */
+static int
+spmi_read_data(struct spmi_device *sdev, uint8_t *buf, int offset, int cnt)
+{
+	int ret = 0;
+	int len;
+	uint16_t addr;
+
+	while (cnt > 0) {
+		addr = offset & 0xFFFF;
+		len = min(cnt, MAX_REG_PER_TRANSACTION);
+
+		ret = spmi_ext_register_readl(sdev, addr, buf, len);
+		if (ret < 0) {
+			dev_err(&sdev->dev,
+				"SPMI read failed, err = %d\n", ret);
+			goto done;
+		}
+
+		cnt -= len;
+		buf += len;
+		offset += len;
+	}
+
+done:
+	return ret;
+}
+
+/**
+ * spmi_write_data: writes data across the SPMI bus
+ * @ctrl: The SPMI controller
+ * @buf: data to be written.
+ * @offset: SPMI address offset to start writing to.
+ * @cnt: The number of bytes to write.
+ *
+ * Returns 0 on success, otherwise returns error code from SPMI driver.
+ */
+static int
+spmi_write_data(struct spmi_device *sdev, uint8_t *buf, int offset, int cnt)
+{
+	int ret = 0;
+	int len;
+	uint16_t addr;
+
+	while (cnt > 0) {
+		addr = offset & 0xFFFF;
+		len = min(cnt, MAX_REG_PER_TRANSACTION);
+
+		ret = spmi_ext_register_writel(sdev, addr, buf, len);
+		if (ret < 0) {
+			dev_err(&sdev->dev,
+				"SPMI write failed, err = %d\n", ret);
+			goto done;
+		}
+
+		cnt -= len;
+		buf += len;
+		offset += len;
+	}
+
+done:
+	return ret;
+}
+
+/**
+ * print_to_log: format a string and place into the log buffer
+ * @log: The log buffer to place the result into.
+ * @fmt: The format string to use.
+ * @...: The arguments for the format string.
+ *
+ * The return value is the number of characters written to @log buffer
+ * not including the trailing '\0'.
+ */
+static int print_to_log(struct spmi_log_buffer *log, const char *fmt, ...)
+{
+	va_list args;
+	int cnt;
+	char *buf = &log->data[log->wpos];
+	size_t size = log->len - log->wpos;
+
+	va_start(args, fmt);
+	cnt = vscnprintf(buf, size, fmt, args);
+	va_end(args);
+
+	log->wpos += cnt;
+	return cnt;
+}
+
+/**
+ * write_next_line_to_log: Writes a single "line" of data into the log buffer
+ * @trans: Pointer to SPMI transaction data.
+ * @offset: SPMI address offset to start reading from.
+ * @pcnt: Pointer to 'cnt' variable.  Indicates the number of bytes to read.
+ *
+ * The 'offset' is a 20-bits SPMI address which includes a 4-bit slave id (SID),
+ * an 8-bit peripheral id (PID), and an 8-bit peripheral register address.
+ *
+ * On a successful read, the pcnt is decremented by the number of data
+ * bytes read across the SPMI bus.  When the cnt reaches 0, all requested
+ * bytes have been read.
+ */
+static int
+write_next_line_to_log(struct spmi_trans *trans, int offset, size_t *pcnt)
+{
+	int i, j;
+	u8  data[ITEMS_PER_LINE];
+	struct spmi_log_buffer *log = trans->log;
+
+	int cnt = 0;
+	int padding = offset % ITEMS_PER_LINE;
+	int items_to_read = min(ARRAY_SIZE(data) - padding, *pcnt);
+	int items_to_log = min(ITEMS_PER_LINE, padding + items_to_read);
+
+	/* Buffer needs enough space for an entire line */
+	if ((log->len - log->wpos) < MAX_LINE_LENGTH)
+		goto done;
+
+	/* Read the desired number of "items" */
+	if (spmi_read_data(trans->sdev, data, offset, items_to_read))
+		goto done;
+
+	*pcnt -= items_to_read;
+
+	/* Each line starts with the aligned offset (20-bit address) */
+	cnt = print_to_log(log, "%5.5X ", offset & 0xffff0);
+	if (cnt == 0)
+		goto done;
+
+	/* If the offset is unaligned, add padding to right justify items */
+	for (i = 0; i < padding; ++i) {
+		cnt = print_to_log(log, "-- ");
+		if (cnt == 0)
+			goto done;
+	}
+
+	/* Log the data items */
+	for (j = 0; i < items_to_log; ++i, ++j) {
+		cnt = print_to_log(log, "%2.2X ", data[j]);
+		if (cnt == 0)
+			goto done;
+	}
+
+	/* If the last character was a space, then replace it with a newline */
+	if (log->wpos > 0 && log->data[log->wpos - 1] == ' ')
+		log->data[log->wpos - 1] = '\n';
+
+done:
+	return cnt;
+}
+
+/**
+ * write_raw_data_to_log: Writes a single "line" of data into the log buffer
+ * @trans: Pointer to SPMI transaction data.
+ * @offset: SPMI address offset to start reading from.
+ * @pcnt: Pointer to 'cnt' variable.  Indicates the number of bytes to read.
+ *
+ * The 'offset' is a 20-bits SPMI address which includes a 4-bit slave id (SID),
+ * an 8-bit peripheral id (PID), and an 8-bit peripheral register address.
+ *
+ * On a successful read, the pcnt is decremented by the number of data
+ * bytes read across the SPMI bus.  When the cnt reaches 0, all requested
+ * bytes have been read.
+ */
+static int
+write_raw_data_to_log(struct spmi_trans *trans, int offset, size_t *pcnt)
+{
+	u8  data[16];
+	struct spmi_log_buffer *log = trans->log;
+
+	int i;
+	int cnt = 0;
+	int items_to_read = min(ARRAY_SIZE(data), *pcnt);
+
+	/* Buffer needs enough space for an entire line */
+	if ((log->len - log->wpos) < 80)
+		goto done;
+
+	/* Read the desired number of "items" */
+	if (spmi_read_data(trans->sdev, data, offset, items_to_read))
+		goto done;
+
+	*pcnt -= items_to_read;
+
+	/* Log the data items */
+	for (i = 0; i < items_to_read; ++i) {
+		cnt = print_to_log(log, "0x%2.2X ", data[i]);
+		if (cnt == 0)
+			goto done;
+	}
+
+	/* If the last character was a space, then replace it with a newline */
+	if (log->wpos > 0 && log->data[log->wpos - 1] == ' ')
+		log->data[log->wpos - 1] = '\n';
+
+done:
+	return cnt;
+}
+
+/**
+ * get_log_data - reads data across the SPMI bus and saves to the log buffer
+ * @trans: Pointer to SPMI transaction data.
+ *
+ * Returns the number of "items" read or SPMI error code for read failures.
+ */
+static int get_log_data(struct spmi_trans *trans)
+{
+	int cnt;
+	int last_cnt;
+	int items_read;
+	int total_items_read = 0;
+	u32 offset = trans->offset;
+	size_t item_cnt = trans->cnt;
+	struct spmi_log_buffer *log = trans->log;
+	int (*write_to_log)(struct spmi_trans *, int, size_t *);
+
+	if (item_cnt == 0)
+		return 0;
+
+	if (trans->raw_data)
+		write_to_log = write_raw_data_to_log;
+	else
+		write_to_log = write_next_line_to_log;
+
+	/* Reset the log buffer 'pointers' */
+	log->wpos = log->rpos = 0;
+
+	/* Keep reading data until the log is full */
+	do {
+		last_cnt = item_cnt;
+		cnt = write_to_log(trans, offset, &item_cnt);
+		items_read = last_cnt - item_cnt;
+		offset += items_read;
+		total_items_read += items_read;
+	} while (cnt && item_cnt > 0);
+
+	/* Adjust the transaction offset and count */
+	trans->cnt = item_cnt;
+	trans->offset += total_items_read;
+
+	return total_items_read;
+}
+
+static ssize_t spmi_device_dfs_reg_write(struct file *file,
+					 const char __user *buf,
+					 size_t count, loff_t *ppos)
+{
+	int bytes_read;
+	int data;
+	int pos = 0;
+	int cnt = 0;
+	u8  *values;
+	size_t ret = 0;
+
+	struct spmi_trans *trans = file->private_data;
+	struct spmi_device *sdev = trans->sdev;
+	u32 offset = trans->offset;
+
+	/* Make a copy of the user data */
+	char *kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	if (copy_from_user(kbuf, buf, count)) {
+		ret = -EFAULT;
+		goto free_buf;
+	}
+
+	*ppos += count;
+	kbuf[count] = '\0';
+
+	/* Override the text buffer with the raw data */
+	values = kbuf;
+
+	/* Parse the data in the buffer.  It should be a string of numbers */
+	while (sscanf(kbuf + pos, "%i%n", &data, &bytes_read) == 1) {
+		pos += bytes_read;
+		values[cnt++] = data & 0xff;
+	}
+
+	if (!cnt)
+		goto free_buf;
+
+	/* Perform the SPMI write(s) */
+	ret = spmi_write_data(trans->sdev, values, offset, cnt);
+
+	if (ret) {
+		dev_err(&sdev->dev, "SPMI write failed, err = %zu\n", ret);
+	} else {
+		ret = count;
+		trans->offset += cnt;
+	}
+
+free_buf:
+	kfree(kbuf);
+	return ret;
+}
+
+static ssize_t spmi_device_dfs_reg_read(struct file *file, char __user *buf,
+					size_t count, loff_t *ppos)
+{
+	struct spmi_trans *trans = file->private_data;
+	struct spmi_device *sdev = trans->sdev;
+	struct spmi_log_buffer *log = trans->log;
+	size_t len;
+
+	/* Is the the log buffer empty */
+	if (log->rpos >= log->wpos) {
+		if (get_log_data(trans) <= 0)
+			return 0;
+	}
+
+	len = min(count, (size_t) log->wpos - log->rpos);
+
+	if (copy_to_user(buf, &log->data[log->rpos], len))
+		return -EFAULT;
+
+	*ppos += len;
+	log->rpos += len;
+	return len;
+}
+
+static const struct file_operations spmi_dfs_reg_fops = {
+	.open		= spmi_device_dfs_data_open,
+	.release	= spmi_device_dfs_close,
+	.read		= spmi_device_dfs_reg_read,
+	.write		= spmi_device_dfs_reg_write,
+};
+
+static const struct file_operations spmi_dfs_raw_data_fops = {
+	.open		= spmi_device_dfs_raw_data_open,
+	.release	= spmi_device_dfs_close,
+	.read		= spmi_device_dfs_reg_read,
+	.write		= spmi_device_dfs_reg_write,
+};
+
+void spmi_dfs_controller_add(struct spmi_controller *ctrl)
+{
+	ctrl->dfs_dir = debugfs_create_dir(dev_name(&ctrl->dev),
+					   spmi_debug_root);
+	WARN_ON(!ctrl->dfs_dir);
+
+	dev_dbg(&ctrl->dev, "adding debug entries for spmi controller\n");
+}
+
+void spmi_dfs_controller_remove(struct spmi_controller *ctrl)
+{
+	debugfs_remove_recursive(ctrl->dfs_dir);
+}
+
+void spmi_dfs_device_add(struct spmi_device *sdev)
+{
+	struct dentry *file;
+
+	dev_dbg(&sdev->dev, "adding debugfs entries for spmi device\n");
+
+	sdev->dfs_dir = debugfs_create_dir(dev_name(&sdev->dev),
+					   sdev->ctrl->dfs_dir);
+	if (WARN_ON(!sdev->dfs_dir))
+		return;
+
+	sdev->dfs_cnt  = 1;
+
+	file = debugfs_create_u32("count", DFS_MODE, sdev->dfs_dir,
+				  &sdev->dfs_cnt);
+	if (WARN_ON(!file))
+		goto err_remove_fs;
+
+	file = debugfs_create_x32("address", DFS_MODE, sdev->dfs_dir,
+				  &sdev->dfs_addr);
+	if (WARN_ON(!file))
+		goto err_remove_fs;
+
+	file = debugfs_create_file("data", DFS_MODE, sdev->dfs_dir, sdev,
+				   &spmi_dfs_reg_fops);
+	if (WARN_ON(!file))
+		goto err_remove_fs;
+
+	file = debugfs_create_file("data_raw", DFS_MODE, sdev->dfs_dir,
+				   sdev, &spmi_dfs_raw_data_fops);
+	if (WARN_ON(!file))
+		goto err_remove_fs;
+
+	return;
+
+err_remove_fs:
+	debugfs_remove_recursive(sdev->dfs_dir);
+}
+
+void spmi_dfs_device_remove(struct spmi_device *sdev)
+{
+	dev_dbg(&sdev->dev, "Deleting device\n");
+	debugfs_remove_recursive(sdev->dfs_dir);
+}
+
+void __exit spmi_dfs_exit(void)
+{
+	debugfs_remove_recursive(spmi_debug_root);
+}
+
+void __init spmi_dfs_init(void)
+{
+	struct dentry *help;
+
+	spmi_debug_root = debugfs_create_dir("spmi", NULL);
+
+	help = debugfs_create_blob("help", S_IRUGO, spmi_debug_root,
+				   &spmi_debug_help);
+
+	WARN_ON(!spmi_debug_root || !help);
+}
+
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/spmi/spmi-dbgfs.h b/drivers/spmi/spmi-dbgfs.h
new file mode 100644
index 0000000..d3162fb
--- /dev/null
+++ b/drivers/spmi/spmi-dbgfs.h
@@ -0,0 +1,25 @@ 
+/* Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
+ *
+ * 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.
+ */
+#ifndef _SPMI_DBGFS_H
+#define _SPMI_DBGFS_H
+
+struct spmi_controller;
+struct spmi_device;
+
+void __init spmi_dfs_init(void);
+void __exit spmi_dfs_exit(void);
+void spmi_dfs_controller_add(struct spmi_controller *ctrl);
+void spmi_dfs_controller_remove(struct spmi_controller *ctrl);
+void spmi_dfs_device_add(struct spmi_device *sdev);
+void spmi_dfs_device_remove(struct spmi_device *sdev);
+
+#endif /* _SPMI_DBGFS_H */
diff --git a/drivers/spmi/spmi.c b/drivers/spmi/spmi.c
new file mode 100644
index 0000000..c3da65e
--- /dev/null
+++ b/drivers/spmi/spmi.c
@@ -0,0 +1,491 @@ 
+/* Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
+ *
+ * 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/kernel.h>
+#include <linux/errno.h>
+#include <linux/idr.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/spmi.h>
+#include <linux/module.h>
+#include <linux/pm_runtime.h>
+
+#include "spmi-dbgfs.h"
+
+static DEFINE_MUTEX(ctrl_idr_lock);
+static DEFINE_IDR(ctrl_idr);
+
+static void spmi_dev_release(struct device *dev)
+{
+	struct spmi_device *sdev = to_spmi_device(dev);
+	spmi_dfs_device_remove(sdev);
+	kfree(sdev);
+}
+
+static struct device_type spmi_dev_type = {
+	.release	= spmi_dev_release,
+};
+
+static void spmi_ctrl_release(struct device *dev)
+{
+	struct spmi_controller *ctrl = to_spmi_controller(dev);
+	spmi_dfs_controller_remove(ctrl);
+	mutex_lock(&ctrl_idr_lock);
+	idr_remove(&ctrl_idr, ctrl->nr);
+	mutex_unlock(&ctrl_idr_lock);
+	kfree(ctrl);
+}
+
+static struct device_type spmi_ctrl_type = {
+	.release	= spmi_ctrl_release,
+};
+
+#ifdef CONFIG_PM_SLEEP
+static int spmi_pm_suspend(struct device *dev)
+{
+	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
+
+	if (pm)
+		return pm_generic_suspend(dev);
+	else
+		return 0;
+}
+
+static int spmi_pm_resume(struct device *dev)
+{
+	const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
+
+	if (pm)
+		return pm_generic_resume(dev);
+	else
+		return 0;
+}
+#else
+#define spmi_pm_suspend		NULL
+#define spmi_pm_resume		NULL
+#endif
+
+static const struct dev_pm_ops spmi_pm_ops = {
+	.suspend	= spmi_pm_suspend,
+	.resume		= spmi_pm_resume,
+	SET_RUNTIME_PM_OPS(
+		pm_generic_suspend,
+		pm_generic_resume,
+		pm_generic_runtime_idle
+	)
+};
+
+static int spmi_device_match(struct device *dev, struct device_driver *drv)
+{
+	if (of_driver_match_device(dev, drv))
+		return 1;
+
+	if (drv->name)
+		return strncmp(dev_name(dev), drv->name,
+			       SPMI_NAME_SIZE) == 0;
+
+	return 0;
+}
+
+int spmi_device_add(struct spmi_device *sdev)
+{
+	struct spmi_controller *ctrl = sdev->ctrl;
+	int err;
+
+	dev_set_name(&sdev->dev, "%d-%02x", ctrl->nr, sdev->usid);
+
+	err = device_add(&sdev->dev);
+	if (err < 0) {
+		dev_err(&sdev->dev, "Can't add %s, status %d\n",
+			dev_name(&sdev->dev), err);
+		goto err_device_add;
+	}
+
+	spmi_dfs_device_add(sdev);
+
+	dev_dbg(&sdev->dev, "device %s registered\n", dev_name(&sdev->dev));
+
+err_device_add:
+	return err;
+}
+EXPORT_SYMBOL_GPL(spmi_device_add);
+
+void spmi_device_remove(struct spmi_device *sdev)
+{
+	device_unregister(&sdev->dev);
+}
+EXPORT_SYMBOL_GPL(spmi_device_remove);
+
+static inline int
+spmi_cmd(struct spmi_controller *ctrl, u8 opcode, u8 sid)
+{
+	if (!ctrl || !ctrl->cmd || ctrl->dev.type != &spmi_ctrl_type)
+		return -EINVAL;
+
+	return ctrl->cmd(ctrl, opcode, sid);
+}
+
+static inline int spmi_read_cmd(struct spmi_controller *ctrl,
+				u8 opcode, u8 sid, u16 addr, u8 bc, u8 *buf)
+{
+	if (!ctrl || !ctrl->read_cmd || ctrl->dev.type != &spmi_ctrl_type)
+		return -EINVAL;
+
+	return ctrl->read_cmd(ctrl, opcode, sid, addr, bc, buf);
+}
+
+static inline int spmi_write_cmd(struct spmi_controller *ctrl,
+				 u8 opcode, u8 sid, u16 addr, u8 bc, u8 *buf)
+{
+	if (!ctrl || !ctrl->write_cmd || ctrl->dev.type != &spmi_ctrl_type)
+		return -EINVAL;
+
+	return ctrl->write_cmd(ctrl, opcode, sid, addr, bc, buf);
+}
+
+/*
+ * register read/write: 5-bit address, 1 byte of data
+ * extended register read/write: 8-bit address, up to 16 bytes of data
+ * extended register read/write long: 16-bit address, up to 8 bytes of data
+ */
+
+int spmi_register_read(struct spmi_device *sdev, u8 addr, u8 *buf)
+{
+	/* 5-bit register address */
+	if (addr > 0x1F)
+		return -EINVAL;
+
+	return spmi_read_cmd(sdev->ctrl, SPMI_CMD_READ, sdev->usid, addr, 0,
+			     buf);
+}
+EXPORT_SYMBOL_GPL(spmi_register_read);
+
+int spmi_ext_register_read(struct spmi_device *sdev, u8 addr, u8 *buf,
+			   size_t len)
+{
+	/* 8-bit register address, up to 16 bytes */
+	if (len == 0 || len > 16)
+		return -EINVAL;
+
+	return spmi_read_cmd(sdev->ctrl, SPMI_CMD_EXT_READ, sdev->usid, addr,
+			     len - 1, buf);
+}
+EXPORT_SYMBOL_GPL(spmi_ext_register_read);
+
+int spmi_ext_register_readl(struct spmi_device *sdev, u16 addr, u8 *buf,
+			    size_t len)
+{
+	/* 16-bit register address, up to 8 bytes */
+	if (len == 0 || len > 8)
+		return -EINVAL;
+
+	return spmi_read_cmd(sdev->ctrl, SPMI_CMD_EXT_READL, sdev->usid, addr,
+			     len - 1, buf);
+}
+EXPORT_SYMBOL_GPL(spmi_ext_register_readl);
+
+int spmi_register_write(struct spmi_device *sdev, u8 addr, u8 *buf)
+{
+	/* 5-bit register address */
+	if (addr > 0x1F)
+		return -EINVAL;
+
+	return spmi_write_cmd(sdev->ctrl, SPMI_CMD_WRITE, sdev->usid, addr, 0,
+			      buf);
+}
+EXPORT_SYMBOL_GPL(spmi_register_write);
+
+int spmi_register_zero_write(struct spmi_device *sdev, u8 data)
+{
+	return spmi_write_cmd(sdev->ctrl, SPMI_CMD_ZERO_WRITE, sdev->usid, 0,
+			      0, &data);
+}
+EXPORT_SYMBOL_GPL(spmi_register_zero_write);
+
+int spmi_ext_register_write(struct spmi_device *sdev, u8 addr, u8 *buf,
+			    size_t len)
+{
+	/* 8-bit register address, up to 16 bytes */
+	if (len == 0 || len > 16)
+		return -EINVAL;
+
+	return spmi_write_cmd(sdev->ctrl, SPMI_CMD_EXT_WRITE, sdev->usid, addr,
+			      len - 1, buf);
+}
+EXPORT_SYMBOL_GPL(spmi_ext_register_write);
+
+int spmi_ext_register_writel(struct spmi_device *sdev, u16 addr, u8 *buf,
+			     size_t len)
+{
+	/* 4-bit Slave Identifier, 16-bit register address, up to 8 bytes */
+	if (len == 0 || len > 8)
+		return -EINVAL;
+
+	return spmi_write_cmd(sdev->ctrl, SPMI_CMD_EXT_WRITEL, sdev->usid,
+			      addr, len - 1, buf);
+}
+EXPORT_SYMBOL_GPL(spmi_ext_register_writel);
+
+int spmi_command_reset(struct spmi_device *sdev)
+{
+	return spmi_cmd(sdev->ctrl, SPMI_CMD_RESET, sdev->usid);
+}
+EXPORT_SYMBOL_GPL(spmi_command_reset);
+
+int spmi_command_sleep(struct spmi_device *sdev)
+{
+	return spmi_cmd(sdev->ctrl, SPMI_CMD_SLEEP, sdev->usid);
+}
+EXPORT_SYMBOL_GPL(spmi_command_sleep);
+
+int spmi_command_wakeup(struct spmi_device *sdev)
+{
+	return spmi_cmd(sdev->ctrl, SPMI_CMD_WAKEUP, sdev->usid);
+}
+EXPORT_SYMBOL_GPL(spmi_command_wakeup);
+
+int spmi_command_shutdown(struct spmi_device *sdev)
+{
+	return spmi_cmd(sdev->ctrl, SPMI_CMD_SHUTDOWN, sdev->usid);
+}
+EXPORT_SYMBOL_GPL(spmi_command_shutdown);
+
+static int spmi_drv_probe(struct device *dev)
+{
+	const struct spmi_driver *sdrv = to_spmi_driver(dev->driver);
+	int err = 0;
+
+	if (sdrv->probe)
+		err = sdrv->probe(to_spmi_device(dev));
+
+	return err;
+}
+
+static int spmi_drv_remove(struct device *dev)
+{
+	const struct spmi_driver *sdrv = to_spmi_driver(dev->driver);
+	int err = 0;
+
+	if (sdrv->remove)
+		err = sdrv->remove(to_spmi_device(dev));
+
+	return err;
+}
+
+static void spmi_drv_shutdown(struct device *dev)
+{
+	const struct spmi_driver *sdrv = to_spmi_driver(dev->driver);
+
+	if (sdrv->shutdown)
+		sdrv->shutdown(to_spmi_device(dev));
+}
+
+static struct bus_type spmi_bus_type = {
+	.name		= "spmi",
+	.match		= spmi_device_match,
+	.pm		= &spmi_pm_ops,
+	.probe		= spmi_drv_probe,
+	.remove		= spmi_drv_remove,
+	.shutdown	= spmi_drv_shutdown,
+};
+
+struct spmi_device *spmi_device_alloc(struct spmi_controller *ctrl)
+{
+	struct spmi_device *sdev;
+
+	sdev = kzalloc(sizeof(*sdev), GFP_KERNEL);
+	if (!sdev)
+		return NULL;
+
+	sdev->ctrl = ctrl;
+	device_initialize(&sdev->dev);
+	sdev->dev.parent = &ctrl->dev;
+	sdev->dev.bus = &spmi_bus_type;
+	sdev->dev.type = &spmi_dev_type;
+	return sdev;
+}
+EXPORT_SYMBOL_GPL(spmi_device_alloc);
+
+struct spmi_controller *spmi_controller_alloc(struct device *parent,
+					      size_t size)
+{
+	struct spmi_controller *ctrl;
+	int id;
+
+	if (WARN_ON(!parent))
+		return NULL;
+
+	ctrl = kzalloc(sizeof(*ctrl) + size, GFP_KERNEL);
+	if (!ctrl)
+		return NULL;
+
+	device_initialize(&ctrl->dev);
+	ctrl->dev.type = &spmi_ctrl_type;
+	ctrl->dev.bus = &spmi_bus_type;
+	ctrl->dev.parent = parent;
+	ctrl->dev.of_node = parent->of_node;
+	spmi_controller_set_drvdata(ctrl, &ctrl[1]);
+
+	idr_preload(GFP_KERNEL);
+	mutex_lock(&ctrl_idr_lock);
+	id = idr_alloc(&ctrl_idr, ctrl, 0, 0, GFP_NOWAIT);
+	mutex_unlock(&ctrl_idr_lock);
+	idr_preload_end();
+
+	if (id < 0) {
+		dev_err(parent,
+			"unable to allocate SPMI controller identifier.\n");
+		spmi_controller_put(ctrl);
+		return NULL;
+	}
+
+	ctrl->nr = id;
+	dev_set_name(&ctrl->dev, "spmi-%d", id);
+
+	dev_dbg(&ctrl->dev, "allocated controller 0x%p id %d\n", ctrl, id);
+	return ctrl;
+}
+EXPORT_SYMBOL_GPL(spmi_controller_alloc);
+
+static int of_spmi_register_devices(struct spmi_controller *ctrl)
+{
+	struct device_node *node;
+	int err;
+
+	dev_dbg(&ctrl->dev, "of_spmi_register_devices\n");
+
+	if (!ctrl->dev.of_node)
+		return -ENODEV;
+
+	dev_dbg(&ctrl->dev, "looping through children\n");
+
+	for_each_available_child_of_node(ctrl->dev.of_node, node) {
+		struct spmi_device *sdev;
+		u32 usid;
+
+		dev_dbg(&ctrl->dev, "adding child %s\n", node->full_name);
+
+		err = of_property_read_u32(node, "reg", &usid);
+		if (err) {
+			dev_err(&ctrl->dev,
+				"node %s does not have 'reg' property\n",
+				node->full_name);
+			continue;
+		}
+
+		if (usid > 0xFF) {
+			dev_err(&ctrl->dev,
+				"invalid usid on node %s\n",
+				node->full_name);
+			continue;
+		}
+
+		dev_dbg(&ctrl->dev, "read usid %02x\n", usid);
+
+		sdev = spmi_device_alloc(ctrl);
+		if (!sdev)
+			continue;
+
+		sdev->dev.of_node = node;
+		sdev->usid = (u8) usid;
+
+		err = spmi_device_add(sdev);
+		if (err) {
+			dev_err(&sdev->dev,
+				"failure adding device. status %d\n", err);
+			spmi_device_put(sdev);
+			continue;
+		}
+	}
+
+	return 0;
+}
+
+int spmi_controller_add(struct spmi_controller *ctrl)
+{
+	int ret;
+
+	/* Can't register until after driver model init */
+	if (WARN_ON(!spmi_bus_type.p))
+		return -EAGAIN;
+
+	ret = device_add(&ctrl->dev);
+	if (ret)
+		return ret;
+
+	spmi_dfs_controller_add(ctrl);
+
+	if (IS_ENABLED(CONFIG_OF))
+		of_spmi_register_devices(ctrl);
+
+	dev_dbg(&ctrl->dev, "spmi-%d registered: dev:%p\n",
+		ctrl->nr, &ctrl->dev);
+
+	return 0;
+};
+EXPORT_SYMBOL_GPL(spmi_controller_add);
+
+/* Remove a device associated with a controller */
+static int spmi_ctrl_remove_device(struct device *dev, void *data)
+{
+	struct spmi_device *spmidev = to_spmi_device(dev);
+	if (dev->type == &spmi_dev_type)
+		spmi_device_remove(spmidev);
+	return 0;
+}
+
+/**
+ * spmi_controller_remove: Controller tear-down.
+ * @ctrl: controller to be removed.
+ *
+ * Controller added with the above API is torn down using this API.
+ */
+int spmi_controller_remove(struct spmi_controller *ctrl)
+{
+	int dummy;
+
+	if (!ctrl)
+		return -EINVAL;
+
+	dummy = device_for_each_child(&ctrl->dev, NULL,
+				      spmi_ctrl_remove_device);
+	device_unregister(&ctrl->dev);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spmi_controller_remove);
+
+int spmi_driver_register(struct spmi_driver *drv)
+{
+	drv->driver.bus = &spmi_bus_type;
+	return driver_register(&drv->driver);
+}
+EXPORT_SYMBOL_GPL(spmi_driver_register);
+
+static void __exit spmi_exit(void)
+{
+	bus_unregister(&spmi_bus_type);
+	spmi_dfs_exit();
+}
+module_exit(spmi_exit);
+
+static int __init spmi_init(void)
+{
+	spmi_dfs_init();
+	return bus_register(&spmi_bus_type);
+}
+postcore_initcall(spmi_init);
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("SPMI module");
+MODULE_ALIAS("platform:spmi");
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 45e9214..677e474 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -432,6 +432,14 @@  struct spi_device_id {
 	kernel_ulong_t driver_data;	/* Data private to the driver */
 };
 
+#define SPMI_NAME_SIZE	32
+#define SPMI_MODULE_PREFIX "spmi:"
+
+struct spmi_device_id {
+	char name[SPMI_NAME_SIZE];
+	kernel_ulong_t driver_data;	/* Data private to the driver */
+};
+
 /* dmi */
 enum dmi_field {
 	DMI_NONE,
diff --git a/include/linux/spmi.h b/include/linux/spmi.h
new file mode 100644
index 0000000..8b9c232
--- /dev/null
+++ b/include/linux/spmi.h
@@ -0,0 +1,355 @@ 
+/* Copyright (c) 2012-2013, The Linux Foundation. All rights reserved.
+ *
+ * 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.
+ */
+#ifndef _LINUX_SPMI_H
+#define _LINUX_SPMI_H
+
+#include <linux/types.h>
+#include <linux/device.h>
+#include <linux/mod_devicetable.h>
+
+/* Maximum slave identifier */
+#define SPMI_MAX_SLAVE_ID		16
+
+/* SPMI Commands */
+#define SPMI_CMD_EXT_WRITE		0x00
+#define SPMI_CMD_RESET			0x10
+#define SPMI_CMD_SLEEP			0x11
+#define SPMI_CMD_SHUTDOWN		0x12
+#define SPMI_CMD_WAKEUP			0x13
+#define SPMI_CMD_AUTHENTICATE		0x14
+#define SPMI_CMD_MSTR_READ		0x15
+#define SPMI_CMD_MSTR_WRITE		0x16
+#define SPMI_CMD_TRANSFER_BUS_OWNERSHIP	0x1A
+#define SPMI_CMD_DDB_MASTER_READ	0x1B
+#define SPMI_CMD_DDB_SLAVE_READ		0x1C
+#define SPMI_CMD_EXT_READ		0x20
+#define SPMI_CMD_EXT_WRITEL		0x30
+#define SPMI_CMD_EXT_READL		0x38
+#define SPMI_CMD_WRITE			0x40
+#define SPMI_CMD_READ			0x60
+#define SPMI_CMD_ZERO_WRITE		0x80
+
+/**
+ * Client/device handle (struct spmi_device):
+ *  This is the client/device handle returned when a SPMI device
+ *  is registered with a controller.
+ *  Pointer to this structure is used by client-driver as a handle.
+ *  @dev: Driver model representation of the device.
+ *  @ctrl: SPMI controller managing the bus hosting this device.
+ *  @usid: Unique Slave IDentifier.
+ *  @dfs_dir: dentry for this device in debugfs
+ *  @dfs_cnt: number of bytes to access for a debugfs operation
+ *  @dfs_addr: address to access for a debugfs operation
+ */
+struct spmi_device {
+	struct device		dev;
+	struct spmi_controller	*ctrl;
+	u8			usid;
+
+#if CONFIG_DEBUG_FS
+	struct dentry		*dfs_dir;
+	u32			dfs_cnt;
+	u32			dfs_addr;
+#endif
+};
+#define to_spmi_device(d) container_of(d, struct spmi_device, dev)
+
+static inline void *spmi_device_get_drvdata(const struct spmi_device *sdev)
+{
+	return dev_get_drvdata(&sdev->dev);
+}
+
+static inline void spmi_device_set_drvdata(struct spmi_device *sdev, void *data)
+{
+	dev_set_drvdata(&sdev->dev, data);
+}
+
+/**
+ * spmi_controller_alloc: Allocate a new SPMI controller
+ * @ctrl: associated controller
+ *
+ * Caller is responsible for either calling spmi_device_add() to add the
+ * newly allocated controller, or calling spmi_device_put() to discard it.
+ */
+struct spmi_device *spmi_device_alloc(struct spmi_controller *ctrl);
+
+static inline void spmi_device_put(struct spmi_device *sdev)
+{
+	if (sdev)
+		put_device(&sdev->dev);
+}
+
+/**
+ * spmi_device_add: add a device previously constructed via spmi_device_alloc()
+ * @sdev: spmi_device to be added
+ */
+int spmi_device_add(struct spmi_device *sdev);
+
+/**
+ * spmi_device_remove: remove a device
+ * @sdev: spmi_device to be removed
+ */
+void spmi_device_remove(struct spmi_device *sdev);
+
+/**
+ * struct spmi_controller: interface to the SPMI master controller
+ * @dev: Driver model representation of the device.
+ * @nr: board-specific number identifier for this controller/bus
+ * @cmd: sends a non-data command sequence on the SPMI bus.
+ * @read_cmd: sends a register read command sequence on the SPMI bus.
+ * @write_cmd: sends a register write command sequence on the SPMI bus.
+ * @dfs_dir: dentry for controller directory in debugfs
+ */
+struct spmi_controller {
+	struct device		dev;
+	unsigned int		nr;
+	int	(*cmd)(struct spmi_controller *ctrl, u8 opcode, u8 sid);
+	int	(*read_cmd)(struct spmi_controller *ctrl, u8 opcode,
+			    u8 sid, u16 addr, u8 bc, u8 *buf);
+	int	(*write_cmd)(struct spmi_controller *ctrl, u8 opcode,
+			     u8 sid, u16 addr, u8 bc, u8 *buf);
+#if CONFIG_DEBUG_FS
+	struct dentry		*dfs_dir;
+#endif
+};
+#define to_spmi_controller(d) container_of(d, struct spmi_controller, dev)
+
+static inline
+void *spmi_controller_get_drvdata(const struct spmi_controller *ctrl)
+{
+	return dev_get_drvdata(&ctrl->dev);
+}
+
+static inline void spmi_controller_set_drvdata(struct spmi_controller *ctrl,
+					       void *data)
+{
+	dev_set_drvdata(&ctrl->dev, data);
+}
+
+/**
+ * spmi_controller_alloc: Allocate a new SPMI controller
+ * @parent: parent device
+ * @size: size of private data
+ *
+ * Caller is responsible for either calling spmi_controller_add() to add the
+ * newly allocated controller, or calling spmi_controller_put() to discard it.
+ */
+struct spmi_controller *spmi_controller_alloc(struct device *parent,
+					      size_t size);
+
+static inline void spmi_controller_put(struct spmi_controller *ctrl)
+{
+	if (ctrl)
+		put_device(&ctrl->dev);
+}
+
+/**
+ * spmi_controller_add: Controller bring-up.
+ * @ctrl: controller to be registered.
+ *
+ * Register a controller previously allocated via spmi_controller_alloc() with
+ * the SPMI core
+ */
+int spmi_controller_add(struct spmi_controller *ctrl);
+
+/**
+ * spmi_controller_remove: Controller tear-down.
+ *
+ * Remove a SPMI controller.
+ */
+int spmi_controller_remove(struct spmi_controller *ctrl);
+
+/**
+ * struct spmi_driver: Manage SPMI generic/slave device driver
+ * @driver: SPMI device drivers should initialize name and owner field of
+ *	    this structure
+ * @probe: binds this driver to a SPMI device.
+ * @remove: unbinds this driver from the SPMI device.
+ * @shutdown: standard shutdown callback used during powerdown/halt.
+ * @suspend: standard suspend callback used during system suspend
+ * @resume: standard resume callback used during system resume
+ */
+struct spmi_driver {
+	struct device_driver driver;
+	int	(*probe)(struct spmi_device *sdev);
+	int	(*remove)(struct spmi_device *sdev);
+	void	(*shutdown)(struct spmi_device *sdev);
+	int	(*suspend)(struct spmi_device *sdev, pm_message_t pmesg);
+	int	(*resume)(struct spmi_device *sdev);
+};
+#define to_spmi_driver(d) container_of(d, struct spmi_driver, driver)
+
+/**
+ * spmi_driver_register: Client driver registration with SPMI framework.
+ * @sdrv: client driver to be associated with client-device.
+ *
+ * This API will register the client driver with the SPMI framework.
+ * It is called from the driver's module-init function.
+ */
+int spmi_driver_register(struct spmi_driver *sdrv);
+
+/**
+ * spmi_driver_unregister - reverse effect of spmi_driver_register
+ * @sdrv: the driver to unregister
+ * Context: can sleep
+ */
+static inline void spmi_driver_unregister(struct spmi_driver *sdrv)
+{
+	if (sdrv)
+		driver_unregister(&sdrv->driver);
+}
+
+#define module_spmi_driver(__spmi_driver) \
+	module_driver(__spmi_driver, spmi_driver_register, \
+			spmi_driver_unregister)
+
+/**
+ * spmi_register_read() - register read
+ * @sdev: SPMI device
+ * @addr: slave register address (5-bit address).
+ * @buf: buffer to be populated with data from the Slave.
+ *
+ * Reads 1 byte of data from a Slave device register.
+ */
+int spmi_register_read(struct spmi_device *sdev, u8 addr, u8 *buf);
+
+/**
+ * spmi_ext_register_read() - extended register read
+ * @sdev: SPMI device
+ * @addr: slave register address (8-bit address).
+ * @buf: buffer to be populated with data from the Slave.
+ * @len: the request number of bytes to read (up to 16 bytes).
+ *
+ * Reads up to 16 bytes of data from the extended register space on a
+ * Slave device.
+ */
+int spmi_ext_register_read(struct spmi_device *sdev, u8 addr, u8 *buf,
+			   size_t len);
+
+/**
+ * spmi_ext_register_readl() - extended register read long
+ * @sdev: SPMI device
+ * @addr: slave register address (16-bit address).
+ * @buf: buffer to be populated with data from the Slave.
+ * @len: the request number of bytes to read (up to 8 bytes).
+ *
+ * Reads up to 8 bytes of data from the extended register space on a
+ * Slave device using 16-bit address.
+ */
+int spmi_ext_register_readl(struct spmi_device *sdev, u16 addr, u8 *buf,
+			    size_t len);
+
+/**
+ * spmi_register_write() - register write
+ * @sdev: SPMI device
+ * @addr: slave register address (5-bit address).
+ * @buf: buffer containing the data to be transferred to the Slave.
+ *
+ * Writes 1 byte of data to a Slave device register.
+ */
+int spmi_register_write(struct spmi_device *sdev, u8 addr, u8 *buf);
+
+/**
+ * spmi_register_zero_write() - register zero write
+ * @sdev: SPMI device
+ * @data: the data to be written to register 0 (7-bits).
+ *
+ * Writes data to register 0 of the Slave device.
+ */
+int spmi_register_zero_write(struct spmi_device *sdev, u8 data);
+
+/**
+ * spmi_ext_register_write() - extended register write
+ * @sdev: SPMI device
+ * @addr: slave register address (8-bit address).
+ * @buf: buffer containing the data to be transferred to the Slave.
+ * @len: the request number of bytes to read (up to 16 bytes).
+ *
+ * Writes up to 16 bytes of data to the extended register space of a
+ * Slave device.
+ */
+int spmi_ext_register_write(struct spmi_device *sdev, u8 addr, u8 *buf,
+			    size_t len);
+
+/**
+ * spmi_ext_register_writel() - extended register write long
+ * @sdev: SPMI device
+ * @addr: slave register address (16-bit address).
+ * @buf: buffer containing the data to be transferred to the Slave.
+ * @len: the request number of bytes to read (up to 8 bytes).
+ *
+ * Writes up to 8 bytes of data to the extended register space of a
+ * Slave device using 16-bit address.
+ */
+int spmi_ext_register_writel(struct spmi_device *sdev, u16 addr,
+			     u8 *buf, size_t len);
+
+/**
+ * spmi_command_reset() - sends RESET command to the specified slave
+ * @sdev: SPMI device
+ *
+ * The Reset command initializes the Slave and forces all registers to
+ * their reset values. The Slave shall enter the STARTUP state after
+ * receiving a Reset command.
+ *
+ * Returns
+ * -EINVAL for invalid slave identifier.
+ * -EPERM if the SPMI transaction is denied due to permission issues.
+ * -EIO if the SPMI transaction fails (parity errors, etc).
+ * -ETIMEDOUT if the SPMI transaction times out.
+ */
+int spmi_command_reset(struct spmi_device *sdev);
+
+/**
+ * spmi_command_sleep() - sends SLEEP command to the specified slave
+ * @sdev: SPMI device
+ *
+ * The Sleep command causes the Slave to enter the user defined SLEEP state.
+ *
+ * Returns
+ * -EINVAL for invalid slave identifier.
+ * -EPERM if the SPMI transaction is denied due to permission issues.
+ * -EIO if the SPMI transaction fails (parity errors, etc).
+ * -ETIMEDOUT if the SPMI transaction times out.
+ */
+int spmi_command_sleep(struct spmi_device *sdev);
+
+/**
+ * spmi_command_wakeup() - sends WAKEUP command to the specified slave
+ * @sdev: SPMI device
+ *
+ * The Wakeup command causes the Slave to move from the SLEEP state to
+ * the ACTIVE state.
+ *
+ * Returns
+ * -EINVAL for invalid slave identifier.
+ * -EPERM if the SPMI transaction is denied due to permission issues.
+ * -EIO if the SPMI transaction fails (parity errors, etc).
+ * -ETIMEDOUT if the SPMI transaction times out.
+ */
+int spmi_command_wakeup(struct spmi_device *sdev);
+
+/**
+ * spmi_command_shutdown() - sends SHUTDOWN command to the specified slave
+ * @sdev: SPMI device
+ *
+ * The Shutdown command causes the Slave to enter the SHUTDOWN state.
+ *
+ * Returns
+ * -EINVAL for invalid slave identifier.
+ * -EPERM if the SPMI transaction is denied due to permission issues.
+ * -EIO if the SPMI transaction fails (parity errors, etc).
+ * -ETIMEDOUT if the SPMI transaction times out.
+ */
+int spmi_command_shutdown(struct spmi_device *sdev);
+
+#endif