diff mbox

[v2,3/3] mxs: added driver for OCOTP in i.MX23 and i.MX28

Message ID 1374078460-4126-4-git-send-email-cb@sgoc.de (mailing list archive)
State New, archived
Headers show

Commit Message

Christoph G. Baumann July 17, 2013, 4:27 p.m. UTC
From: "Christoph G. Baumann" <cb@sgoc.de>

Signed-off-by: "Christoph G. Baumann" <cb@sgoc.de>
---
 drivers/misc/Kconfig   |   14 ++
 drivers/misc/Makefile  |    1 +
 drivers/misc/fsl_otp.c |  363 ++++++++++++++++++++++++++++++++++++++++++++++++
 drivers/misc/fsl_otp.h |  126 +++++++++++++++++
 4 files changed, 504 insertions(+)
 create mode 100644 drivers/misc/fsl_otp.c
 create mode 100644 drivers/misc/fsl_otp.h

Comments

Sascha Hauer July 17, 2013, 7:26 p.m. UTC | #1
Hi Christoph,

Several comments inline.

On Wed, Jul 17, 2013 at 06:27:40PM +0200, Christoph G. Baumann wrote:
> From: "Christoph G. Baumann" <cb@sgoc.de>
> 
> Signed-off-by: "Christoph G. Baumann" <cb@sgoc.de>
> ---
>  drivers/misc/Kconfig   |   14 ++
>  drivers/misc/Makefile  |    1 +
>  drivers/misc/fsl_otp.c |  363 ++++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/misc/fsl_otp.h |  126 +++++++++++++++++
>  4 files changed, 504 insertions(+)
>  create mode 100644 drivers/misc/fsl_otp.c
>  create mode 100644 drivers/misc/fsl_otp.h
> 
> diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> index 8dacd4c..0740312 100644
> --- a/drivers/misc/Kconfig
> +++ b/drivers/misc/Kconfig
> @@ -528,6 +528,20 @@ config SRAM
>  	  the genalloc API. It is supposed to be used for small on-chip SRAM
>  	  areas found on many SoCs.
>  
> +config FSL_OTP
> +	tristate "Freescale On-Chip OTP Memory Support"
> +	depends on SOC_IMX23 || SOC_IMX28
> +	default n

default n is the default. You can drop this.

> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
> + */

Please drop the address. It's wrong already.

> +static DEFINE_MUTEX(otp_mutex);
> +static struct kobject *otp_kobj;
> +static struct attribute **attrs;
> +static struct kobj_attribute *kattr;
> +static struct attribute_group attr_group;
> +static unsigned long otp_hclk_saved;
> +static u32 otp_voltage_saved;
> +static resource_size_t otp_base_address;
> +struct regulator *regu;

Collect your driver data in a struct and pass it around in functions
calls. No need to limit this driver to a single instance.

> +/* forward declaration */

Who would have guessed that? Drop this, it contains no information.

> +static int otp_wait_busy(u32 flags);

You should reorder the functions so that forward declarations are not
necessary.

> +
> +/* open the bank for the imx23/imx28 */
> +static int otp_read_prepare(void)
> +{
> +	int r;
> +
> +	/* [1] set the HCLK */
> +	/* [2] check BUSY and ERROR bit */
> +	r = otp_wait_busy(0);
> +	if (r < 0)
> +		goto error;
> +
> +	/* [3] open bank */
> +	__raw_writel(BM_OCOTP_CTRL_RD_BANK_OPEN,
> +		REGS_OCOTP_BASE + HW_OCOTP_CTRL_SET);
> +	udelay(10);
> +
> +	/* [4] wait for BUSY */
> +	r = otp_wait_busy(0);
> +	return 0;
> +error:
> +	return r;
> +}
> +
> +static int otp_read_post(void)
> +{
> +	/* [5] close bank */
> +	__raw_writel(BM_OCOTP_CTRL_RD_BANK_OPEN,
> +		REGS_OCOTP_BASE + HW_OCOTP_CTRL_CLR);
> +	return 0;
> +}
> +
> +static int otp_write_prepare(void)
> +{
> +	struct clk *hclk;
> +	int err = 0;
> +
> +	/* [1] HCLK to 24MHz. */
> +	hclk = clk_get_sys("hbus", NULL);

This is a driver, so you should use regular clk_get, not clk_get_sys.
Besides, this has to be done during probe. clk_get takes a reference to
the clock which has to be released.

> +	if (IS_ERR(hclk)) {
> +		err = PTR_ERR(hclk);
> +		goto out;
> +	}
> +	/*
> +	   WARNING  ACHTUNG  UWAGA
> +
> +	   the code below changes HCLK clock rate to 24M. This is
> +	   required to write OTP bits (7.2.2 in STMP378x Target
> +	   Specification), and might affect LCD operation, for example.
> +	   Moreover, this hacky code changes VDDIO to 2.8V; and resto-
> +	   res it only on otp_close(). This may affect... anything.
> +
> +	   You are warned now.
> +	 */
> +	otp_hclk_saved = clk_get_rate(hclk);
> +	clk_set_rate(hclk, 24000000);

You should check the return value.

> +
> +	/* [2] The voltage is set to 2.8V */
> +	regu = regulator_get(NULL, otp_data.regulator_name);

Same as with clk_get. Do it during probe time.

> +	otp_voltage_saved = regulator_get_voltage(regu);
> +	regulator_set_voltage(regu, 2800000, 2800000);

Check the return value.

> +
> +	/* [3] wait for BUSY and ERROR */
> +	err = otp_wait_busy(BM_OCOTP_CTRL_RD_BANK_OPEN);
> +out:
> +	return err;
> +}
> +
> +static int otp_write_post(void)
> +{
> +	struct clk *hclk;
> +
> +	hclk = clk_get_sys("hbus", NULL);
> +	if (IS_ERR(hclk))
> +		return PTR_ERR(hclk);
> +
> +	/* restore the clock and voltage */
> +	clk_set_rate(hclk, otp_hclk_saved);
> +	regulator_set_voltage(regu, otp_voltage_saved, otp_voltage_saved);
> +	otp_wait_busy(0);
> +
> +	/* reset */
> +	__raw_writel(BM_OCOTP_CTRL_RELOAD_SHADOWS,
> +			REGS_OCOTP_BASE + HW_OCOTP_CTRL_SET);
> +	otp_wait_busy(BM_OCOTP_CTRL_RELOAD_SHADOWS);
> +	return 0;
> +}
> +
> +static int __init map_ocotp_addr(struct platform_device *pdev)
> +{
> +	return 0;
> +}

What's this? Drop this.

> +static void unmap_ocotp_addr(void)
> +{
> +}

ditto

> +
> +static inline unsigned int get_reg_index(struct kobj_attribute *tmp)
> +{
> +	return tmp - kattr;
> +}
> +
> +static int otp_wait_busy(u32 flags)
> +{
> +	int count;
> +	u32 c;
> +
> +	for (count = 10000; count >= 0; count--) {
> +		c = __raw_readl(REGS_OCOTP_BASE + HW_OCOTP_CTRL);
> +		if (!(c & (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR | flags)))
> +			break;
> +		cpu_relax();
> +	}
> +
> +	if (count < 0)
> +		return -ETIMEDOUT;
> +	return 0;
> +}
> +
> +static ssize_t otp_show(struct kobject *kobj, struct kobj_attribute *attr,
> +		      char *buf)
> +{
> +	unsigned int index = get_reg_index(attr);
> +	u32 value = 0;
> +
> +	/* sanity check */
> +	if (index >= otp_data.fuse_num)
> +		return 0;
> +
> +	mutex_lock(&otp_mutex);
> +
> +	if (otp_read_prepare()) {
> +		mutex_unlock(&otp_mutex);
> +		return 0;
> +	}
> +	value = __raw_readl(REGS_OCOTP_BASE + HW_OCOTP_CUST_N(index));
> +	otp_read_post();
> +
> +	mutex_unlock(&otp_mutex);
> +	return sprintf(buf, "0x%x\n", value);
> +}
> +
> +static int otp_write_bits(int addr, u32 data, u32 magic)
> +{
> +	u32 c; /* for control register */
> +
> +	/* init the control register */
> +	c = __raw_readl(REGS_OCOTP_BASE + HW_OCOTP_CTRL);
> +	c &= ~BM_OCOTP_CTRL_ADDR;
> +	c |= BF(addr, OCOTP_CTRL_ADDR);
> +	c |= BF(magic, OCOTP_CTRL_WR_UNLOCK);
> +	__raw_writel(c, REGS_OCOTP_BASE + HW_OCOTP_CTRL);
> +
> +	/* init the data register */
> +	__raw_writel(data, REGS_OCOTP_BASE + HW_OCOTP_DATA);
> +	otp_wait_busy(0);
> +
> +	mdelay(2); /* Write Postamble */
> +	return 0;
> +}
> +
> +static ssize_t otp_store(struct kobject *kobj, struct kobj_attribute *attr,
> +		       const char *buf, size_t count)
> +{
> +	unsigned int index = get_reg_index(attr);
> +	int value;
> +
> +	/* sanity check */
> +	if (index >= otp_data.fuse_num)
> +		return 0;
> +
> +	sscanf(buf, "0x%x", &value);
> +
> +	mutex_lock(&otp_mutex);
> +	if (otp_write_prepare()) {
> +		mutex_unlock(&otp_mutex);
> +		return 0;
> +	}
> +	otp_write_bits(index, value, 0x3e77);
> +	otp_write_post();
> +	mutex_unlock(&otp_mutex);
> +
> +	return count;
> +}
> +
> +static void free_otp_attr(void)
> +{
> +	kfree(attrs);
> +	attrs = NULL;
> +
> +	kfree(kattr);
> +	kattr = NULL;
> +}
> +
> +static int alloc_otp_attr(void)
> +{
> +	int i;
> +
> +	/* The last one is NULL, which is used to detect the end */
> +	attrs = kzalloc((otp_data.fuse_num + 1) * sizeof(attrs[0]),
> +			GFP_KERNEL);
> +	kattr = kzalloc(otp_data.fuse_num * sizeof(struct kobj_attribute),
> +			GFP_KERNEL);
> +
> +	if (!attrs || !kattr)
> +		goto error_out;
> +
> +	for (i = 0; i < otp_data.fuse_num; i++) {
> +		kattr[i].attr.name = otp_data.fuse_name[i];
> +		kattr[i].attr.mode = 0600;
> +		kattr[i].show  = otp_show;
> +		kattr[i].store = otp_store;
> +		attrs[i] = &kattr[i].attr;
> +		sysfs_attr_init(attrs[i]);
> +	}
> +	memset(&attr_group, 0, sizeof(attr_group));
> +	attr_group.attrs = attrs;
> +	return 0;
> +
> +error_out:
> +	free_otp_attr();
> +	return -ENOMEM;
> +}
> +
> +static int fsl_otp_probe(struct platform_device *pdev)
> +{
> +	int retval;
> +	struct fsl_otp_data *pdata;
> +
> +	/* get device base address */
> +	otp_base_address = pdev->resource->start;
> +	dev_info(&pdev->dev, "i.MX23/28 OCOTP at %p\n", otp_base_address);
> +
> +	pdata = &otp_data;
> +	if (pdev->dev.platform_data == NULL)
> +		pdev->dev.platform_data = &otp_data;

You shouldn't manipulate the platform_data pointer in the driver.
platform_data contains data passed to the driver.

> +
> +	retval = alloc_otp_attr();
> +	if (retval)
> +		return retval;
> +
> +	retval = map_ocotp_addr(pdev);
> +	if (retval)
> +		goto error;
> +
> +	otp_kobj = kobject_create_and_add("fsl_otp", NULL);
> +	if (!otp_kobj) {
> +		retval = -ENOMEM;
> +		goto error;
> +	}
> +
> +	retval = sysfs_create_group(otp_kobj, &attr_group);
> +	if (retval)
> +		goto error;
> +
> +	mutex_init(&otp_mutex);
> +	return 0;
> +error:
> +	kobject_put(otp_kobj);
> +	otp_kobj = NULL;
> +	free_otp_attr();
> +	unmap_ocotp_addr();
> +	return retval;
> +}
> +
> +static int otp_remove(struct platform_device *pdev)
> +{
> +	kobject_put(otp_kobj);
> +	otp_kobj = NULL;
> +
> +	free_otp_attr();
> +	unmap_ocotp_addr();
> +	return 0;
> +}
> +
> +static const struct of_device_id mxs_otp_dt_ids[] = {
> +	{ .compatible = "fsl,ocotp", .data = NULL, },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, mxs_otp_dt_ids);
> +
> +static struct platform_driver ocotp_driver = {
> +	.probe		= fsl_otp_probe,
> +	.remove		= otp_remove,
> +	.driver		= {
> +		.name   = "ocotp",
> +		.owner	= THIS_MODULE,
> +		.of_match_table = mxs_otp_dt_ids,
> +	},
> +};
> +
> +static int __init fsl_otp_init(void)
> +{
> +	return platform_driver_register(&ocotp_driver);
> +}
> +
> +static void __exit fsl_otp_exit(void)
> +{
> +	platform_driver_unregister(&ocotp_driver);
> +}
> +module_init(fsl_otp_init);
> +module_exit(fsl_otp_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Christoph G. Baumann <cgb@debian.org>");
> +MODULE_DESCRIPTION("driver for OCOTP in i.MX23 and i.MX28");
> diff --git a/drivers/misc/fsl_otp.h b/drivers/misc/fsl_otp.h
> new file mode 100644
> index 0000000..9449f94
> --- /dev/null
> +++ b/drivers/misc/fsl_otp.h
> @@ -0,0 +1,126 @@
> +/*
> + * Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
> + *
> + * Ported to 3.7 by Christoph G. Baumann <cgb@debian.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * 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.
> + *
> + * You should have received a copy of the GNU General Public License along
> + * with this program; if not, write to the Free Software Foundation, Inc.,
> + * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

Here's another address of the FSF. That's the reason for not including
it.

> + */
> +#ifndef __FREESCALE_OTP__
> +#define __FREESCALE_OTP__
> +
> +
> +/* IMX23 and IMX28 share most of the defination ========================= */
> +#if (defined(CONFIG_SOC_IMX23) || defined(CONFIG_SOC_IMX28))
> +
> +#if defined(CONFIG_SOC_IMX28) && defined(CONFIG_SOC_IMX23)
> +#undef CONFIG_SOC_IMX23
> +#endif

So if the kernel supports both i.MX23 and i.MX28 you choose to make the
driver work on i.MX28 only. You have to make this a runtime decision.
See some other driver how this can be made, for example
drivers/spi/spi-imx.c. Look for the usage of of_match_device().

> +
> +
> +#define OCOTP_PHYS_ADDR         otp_base_address
> +#define REGS_OCOTP_BASE		(MXS_IO_ADDRESS(OCOTP_PHYS_ADDR))

Drop this and use ioremap in the driver.

> +#define BF(value, field)	(((value) << BP_##field) & BM_##field)
> +
> +/* MXS IO mappings */
> +
> +/*
> + * It maps the whole address space to [0xf4000000, 0xf50fffff].
> + *
> + *	OCRAM	0x00000000+0x020000	->	0xf4000000+0x020000
> + *	IO	0x80000000+0x100000	->	0xf5000000+0x100000
> + */
> +#define MXS_IO_P2V(x)	(0xf4000000 +					\
> +			(((x) & 0x80000000) >> 7) +			\
> +			(((x) & 0x000fffff)))
> +
> +#define MXS_IO_ADDRESS(x)	IOMEM(MXS_IO_P2V(x))

This also shouldn't be in a driver.

Sascha
Christoph G. Baumann July 17, 2013, 9:43 p.m. UTC | #2
Hello Sascha,

thanks for your input. I must admit that I didn't do a thorough review of the
FSL code...


> Sascha Hauer <s.hauer@pengutronix.de> hat am 17. Juli 2013 um 21:26
> geschrieben:
> [...]
> > +static DEFINE_MUTEX(otp_mutex);
> > +static struct kobject *otp_kobj;
> > +static struct attribute **attrs;
> > +static struct kobj_attribute *kattr;
> > +static struct attribute_group attr_group;
> > +static unsigned long otp_hclk_saved;
> > +static u32 otp_voltage_saved;
> > +static resource_size_t otp_base_address;
> > +struct regulator *regu;
>
> Collect your driver data in a struct and pass it around in functions
> calls. No need to limit this driver to a single instance.

The OTP device is unique in the CPU and several instances i.e. potential
concurrent access is considered harmful. So I kept this construction
from FSL.


> > +static int otp_write_prepare(void)
> > +{
> > +     struct clk *hclk;
> > +     int err = 0;
> > +
> > +     /* [1] HCLK to 24MHz. */
> > +     hclk = clk_get_sys("hbus", NULL);
>
> This is a driver, so you should use regular clk_get, not clk_get_sys.
> Besides, this has to be done during probe. clk_get takes a reference to
> the clock which has to be released.

As far as I remember testing clk_get didn't work in this place.
In the API doc I only found the warning:
"clk_get_sys should not be called from within interrupt context.".


Regards,
Christoph
Sascha Hauer July 18, 2013, 6:36 a.m. UTC | #3
On Wed, Jul 17, 2013 at 11:43:12PM +0200, Christoph G. Baumann wrote:
> Hello Sascha,
> 
> thanks for your input. I must admit that I didn't do a thorough review of the
> FSL code...
> 
> 
> > Sascha Hauer <s.hauer@pengutronix.de> hat am 17. Juli 2013 um 21:26
> > geschrieben:
> > [...]
> > > +static DEFINE_MUTEX(otp_mutex);
> > > +static struct kobject *otp_kobj;
> > > +static struct attribute **attrs;
> > > +static struct kobj_attribute *kattr;
> > > +static struct attribute_group attr_group;
> > > +static unsigned long otp_hclk_saved;
> > > +static u32 otp_voltage_saved;
> > > +static resource_size_t otp_base_address;
> > > +struct regulator *regu;
> >
> > Collect your driver data in a struct and pass it around in functions
> > calls. No need to limit this driver to a single instance.
> 
> The OTP device is unique in the CPU and several instances i.e. potential
> concurrent access is considered harmful. So I kept this construction
> from FSL.

Yes, this is single instance only in current SoCs. This is no reason
though to make the driver single instance capabable only. It's not
much work to change and it raises less eyebrows if it's properly
written.
In the end I never thought that there ever would be two instances of
the i.MX graphics subsystem (IPU). Now the i.MX6 has two of them...

> 
> 
> > > +static int otp_write_prepare(void)
> > > +{
> > > +     struct clk *hclk;
> > > +     int err = 0;
> > > +
> > > +     /* [1] HCLK to 24MHz. */
> > > +     hclk = clk_get_sys("hbus", NULL);
> >
> > This is a driver, so you should use regular clk_get, not clk_get_sys.
> > Besides, this has to be done during probe. clk_get takes a reference to
> > the clock which has to be released.
> 
> As far as I remember testing clk_get didn't work in this place.

That is because the clk_register_clkdev() in your other patch is wrong.

Look at the 'clocks' and 'clock-names' properties in the devicetree.
Also look at Documentation/devicetree/bindings/clock/imx28-clock.txt.

In short you have to add a clock to your devicetree node and then use
clk_get(). The struct device * passed to clk_get will make the bridge
between the device and the devicenode and the id argument will be the
same name as in the devicetree.

Sascha
Christoph G. Baumann July 18, 2013, 3:14 p.m. UTC | #4
Hello Sascha,

unfortunately I don't have the time at the moment to further fix the FSL code.
Maybe someone else feels inclined?


Regards
Christoph
diff mbox

Patch

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 8dacd4c..0740312 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -528,6 +528,20 @@  config SRAM
 	  the genalloc API. It is supposed to be used for small on-chip SRAM
 	  areas found on many SoCs.
 
+config FSL_OTP
+	tristate "Freescale On-Chip OTP Memory Support"
+	depends on SOC_IMX23 || SOC_IMX28
+	default n
+	help
+		If you say Y here, you will get support for a SysFS interface for
+		the One Time Programmable memory pages that are stored on the
+		iMX23/28 processor.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called fsl_otp.
+
+	  If unsure, it is safe to say N.
+
 source "drivers/misc/c2port/Kconfig"
 source "drivers/misc/eeprom/Kconfig"
 source "drivers/misc/cb710/Kconfig"
diff --git a/drivers/misc/Makefile b/drivers/misc/Makefile
index c235d5b..e622e01 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -53,3 +53,4 @@  obj-$(CONFIG_INTEL_MEI)		+= mei/
 obj-$(CONFIG_VMWARE_VMCI)	+= vmw_vmci/
 obj-$(CONFIG_LATTICE_ECP3_CONFIG)	+= lattice-ecp3-config.o
 obj-$(CONFIG_SRAM)		+= sram.o
+obj-$(CONFIG_FSL_OTP)           += fsl_otp.o
diff --git a/drivers/misc/fsl_otp.c b/drivers/misc/fsl_otp.c
new file mode 100644
index 0000000..7ae6ea0
--- /dev/null
+++ b/drivers/misc/fsl_otp.c
@@ -0,0 +1,363 @@ 
+/*
+ * Freescale On-Chip OTP driver
+ *
+ * Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
+ * Huang Shijie <b32955@freescale.com>
+ *
+ * Ported to 3.x by Christoph G. Baumann <cgb@debian.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+#include <linux/kobject.h>
+#include <linux/string.h>
+#include <linux/sysfs.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/delay.h>
+#include <linux/fcntl.h>
+#include <linux/mutex.h>
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/slab.h>
+#include <linux/platform_device.h>
+#include <linux/regulator/consumer.h>
+
+#include "fsl_otp.h"
+
+static DEFINE_MUTEX(otp_mutex);
+static struct kobject *otp_kobj;
+static struct attribute **attrs;
+static struct kobj_attribute *kattr;
+static struct attribute_group attr_group;
+static unsigned long otp_hclk_saved;
+static u32 otp_voltage_saved;
+static resource_size_t otp_base_address;
+struct regulator *regu;
+
+static struct fsl_otp_data otp_data = {
+	.fuse_name	= (char **)bank_reg_desc,
+	.regulator_name	= "vddio-sd0",
+	.fuse_num	= MXS_OTP_BANKS * MXS_OTP_BANK_ITEMS,
+};
+
+
+/* forward declaration */
+static int otp_wait_busy(u32 flags);
+
+/* open the bank for the imx23/imx28 */
+static int otp_read_prepare(void)
+{
+	int r;
+
+	/* [1] set the HCLK */
+	/* [2] check BUSY and ERROR bit */
+	r = otp_wait_busy(0);
+	if (r < 0)
+		goto error;
+
+	/* [3] open bank */
+	__raw_writel(BM_OCOTP_CTRL_RD_BANK_OPEN,
+		REGS_OCOTP_BASE + HW_OCOTP_CTRL_SET);
+	udelay(10);
+
+	/* [4] wait for BUSY */
+	r = otp_wait_busy(0);
+	return 0;
+error:
+	return r;
+}
+
+static int otp_read_post(void)
+{
+	/* [5] close bank */
+	__raw_writel(BM_OCOTP_CTRL_RD_BANK_OPEN,
+		REGS_OCOTP_BASE + HW_OCOTP_CTRL_CLR);
+	return 0;
+}
+
+static int otp_write_prepare(void)
+{
+	struct clk *hclk;
+	int err = 0;
+
+	/* [1] HCLK to 24MHz. */
+	hclk = clk_get_sys("hbus", NULL);
+	if (IS_ERR(hclk)) {
+		err = PTR_ERR(hclk);
+		goto out;
+	}
+	/*
+	   WARNING  ACHTUNG  UWAGA
+
+	   the code below changes HCLK clock rate to 24M. This is
+	   required to write OTP bits (7.2.2 in STMP378x Target
+	   Specification), and might affect LCD operation, for example.
+	   Moreover, this hacky code changes VDDIO to 2.8V; and resto-
+	   res it only on otp_close(). This may affect... anything.
+
+	   You are warned now.
+	 */
+	otp_hclk_saved = clk_get_rate(hclk);
+	clk_set_rate(hclk, 24000000);
+
+	/* [2] The voltage is set to 2.8V */
+	regu = regulator_get(NULL, otp_data.regulator_name);
+	otp_voltage_saved = regulator_get_voltage(regu);
+	regulator_set_voltage(regu, 2800000, 2800000);
+
+	/* [3] wait for BUSY and ERROR */
+	err = otp_wait_busy(BM_OCOTP_CTRL_RD_BANK_OPEN);
+out:
+	return err;
+}
+
+static int otp_write_post(void)
+{
+	struct clk *hclk;
+
+	hclk = clk_get_sys("hbus", NULL);
+	if (IS_ERR(hclk))
+		return PTR_ERR(hclk);
+
+	/* restore the clock and voltage */
+	clk_set_rate(hclk, otp_hclk_saved);
+	regulator_set_voltage(regu, otp_voltage_saved, otp_voltage_saved);
+	otp_wait_busy(0);
+
+	/* reset */
+	__raw_writel(BM_OCOTP_CTRL_RELOAD_SHADOWS,
+			REGS_OCOTP_BASE + HW_OCOTP_CTRL_SET);
+	otp_wait_busy(BM_OCOTP_CTRL_RELOAD_SHADOWS);
+	return 0;
+}
+
+static int __init map_ocotp_addr(struct platform_device *pdev)
+{
+	return 0;
+}
+static void unmap_ocotp_addr(void)
+{
+}
+
+static inline unsigned int get_reg_index(struct kobj_attribute *tmp)
+{
+	return tmp - kattr;
+}
+
+static int otp_wait_busy(u32 flags)
+{
+	int count;
+	u32 c;
+
+	for (count = 10000; count >= 0; count--) {
+		c = __raw_readl(REGS_OCOTP_BASE + HW_OCOTP_CTRL);
+		if (!(c & (BM_OCOTP_CTRL_BUSY | BM_OCOTP_CTRL_ERROR | flags)))
+			break;
+		cpu_relax();
+	}
+
+	if (count < 0)
+		return -ETIMEDOUT;
+	return 0;
+}
+
+static ssize_t otp_show(struct kobject *kobj, struct kobj_attribute *attr,
+		      char *buf)
+{
+	unsigned int index = get_reg_index(attr);
+	u32 value = 0;
+
+	/* sanity check */
+	if (index >= otp_data.fuse_num)
+		return 0;
+
+	mutex_lock(&otp_mutex);
+
+	if (otp_read_prepare()) {
+		mutex_unlock(&otp_mutex);
+		return 0;
+	}
+	value = __raw_readl(REGS_OCOTP_BASE + HW_OCOTP_CUST_N(index));
+	otp_read_post();
+
+	mutex_unlock(&otp_mutex);
+	return sprintf(buf, "0x%x\n", value);
+}
+
+static int otp_write_bits(int addr, u32 data, u32 magic)
+{
+	u32 c; /* for control register */
+
+	/* init the control register */
+	c = __raw_readl(REGS_OCOTP_BASE + HW_OCOTP_CTRL);
+	c &= ~BM_OCOTP_CTRL_ADDR;
+	c |= BF(addr, OCOTP_CTRL_ADDR);
+	c |= BF(magic, OCOTP_CTRL_WR_UNLOCK);
+	__raw_writel(c, REGS_OCOTP_BASE + HW_OCOTP_CTRL);
+
+	/* init the data register */
+	__raw_writel(data, REGS_OCOTP_BASE + HW_OCOTP_DATA);
+	otp_wait_busy(0);
+
+	mdelay(2); /* Write Postamble */
+	return 0;
+}
+
+static ssize_t otp_store(struct kobject *kobj, struct kobj_attribute *attr,
+		       const char *buf, size_t count)
+{
+	unsigned int index = get_reg_index(attr);
+	int value;
+
+	/* sanity check */
+	if (index >= otp_data.fuse_num)
+		return 0;
+
+	sscanf(buf, "0x%x", &value);
+
+	mutex_lock(&otp_mutex);
+	if (otp_write_prepare()) {
+		mutex_unlock(&otp_mutex);
+		return 0;
+	}
+	otp_write_bits(index, value, 0x3e77);
+	otp_write_post();
+	mutex_unlock(&otp_mutex);
+
+	return count;
+}
+
+static void free_otp_attr(void)
+{
+	kfree(attrs);
+	attrs = NULL;
+
+	kfree(kattr);
+	kattr = NULL;
+}
+
+static int alloc_otp_attr(void)
+{
+	int i;
+
+	/* The last one is NULL, which is used to detect the end */
+	attrs = kzalloc((otp_data.fuse_num + 1) * sizeof(attrs[0]),
+			GFP_KERNEL);
+	kattr = kzalloc(otp_data.fuse_num * sizeof(struct kobj_attribute),
+			GFP_KERNEL);
+
+	if (!attrs || !kattr)
+		goto error_out;
+
+	for (i = 0; i < otp_data.fuse_num; i++) {
+		kattr[i].attr.name = otp_data.fuse_name[i];
+		kattr[i].attr.mode = 0600;
+		kattr[i].show  = otp_show;
+		kattr[i].store = otp_store;
+		attrs[i] = &kattr[i].attr;
+		sysfs_attr_init(attrs[i]);
+	}
+	memset(&attr_group, 0, sizeof(attr_group));
+	attr_group.attrs = attrs;
+	return 0;
+
+error_out:
+	free_otp_attr();
+	return -ENOMEM;
+}
+
+static int fsl_otp_probe(struct platform_device *pdev)
+{
+	int retval;
+	struct fsl_otp_data *pdata;
+
+	/* get device base address */
+	otp_base_address = pdev->resource->start;
+	dev_info(&pdev->dev, "i.MX23/28 OCOTP at %p\n", otp_base_address);
+
+	pdata = &otp_data;
+	if (pdev->dev.platform_data == NULL)
+		pdev->dev.platform_data = &otp_data;
+
+	retval = alloc_otp_attr();
+	if (retval)
+		return retval;
+
+	retval = map_ocotp_addr(pdev);
+	if (retval)
+		goto error;
+
+	otp_kobj = kobject_create_and_add("fsl_otp", NULL);
+	if (!otp_kobj) {
+		retval = -ENOMEM;
+		goto error;
+	}
+
+	retval = sysfs_create_group(otp_kobj, &attr_group);
+	if (retval)
+		goto error;
+
+	mutex_init(&otp_mutex);
+	return 0;
+error:
+	kobject_put(otp_kobj);
+	otp_kobj = NULL;
+	free_otp_attr();
+	unmap_ocotp_addr();
+	return retval;
+}
+
+static int otp_remove(struct platform_device *pdev)
+{
+	kobject_put(otp_kobj);
+	otp_kobj = NULL;
+
+	free_otp_attr();
+	unmap_ocotp_addr();
+	return 0;
+}
+
+static const struct of_device_id mxs_otp_dt_ids[] = {
+	{ .compatible = "fsl,ocotp", .data = NULL, },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, mxs_otp_dt_ids);
+
+static struct platform_driver ocotp_driver = {
+	.probe		= fsl_otp_probe,
+	.remove		= otp_remove,
+	.driver		= {
+		.name   = "ocotp",
+		.owner	= THIS_MODULE,
+		.of_match_table = mxs_otp_dt_ids,
+	},
+};
+
+static int __init fsl_otp_init(void)
+{
+	return platform_driver_register(&ocotp_driver);
+}
+
+static void __exit fsl_otp_exit(void)
+{
+	platform_driver_unregister(&ocotp_driver);
+}
+module_init(fsl_otp_init);
+module_exit(fsl_otp_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Christoph G. Baumann <cgb@debian.org>");
+MODULE_DESCRIPTION("driver for OCOTP in i.MX23 and i.MX28");
diff --git a/drivers/misc/fsl_otp.h b/drivers/misc/fsl_otp.h
new file mode 100644
index 0000000..9449f94
--- /dev/null
+++ b/drivers/misc/fsl_otp.h
@@ -0,0 +1,126 @@ 
+/*
+ * Copyright (C) 2010 Freescale Semiconductor, Inc. All Rights Reserved.
+ *
+ * Ported to 3.7 by Christoph G. Baumann <cgb@debian.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#ifndef __FREESCALE_OTP__
+#define __FREESCALE_OTP__
+
+
+/* IMX23 and IMX28 share most of the defination ========================= */
+#if (defined(CONFIG_SOC_IMX23) || defined(CONFIG_SOC_IMX28))
+
+#if defined(CONFIG_SOC_IMX28) && defined(CONFIG_SOC_IMX23)
+#undef CONFIG_SOC_IMX23
+#endif
+
+
+#define OCOTP_PHYS_ADDR         otp_base_address
+#define REGS_OCOTP_BASE		(MXS_IO_ADDRESS(OCOTP_PHYS_ADDR))
+#define BF(value, field)	(((value) << BP_##field) & BM_##field)
+
+/* MXS IO mappings */
+
+/*
+ * It maps the whole address space to [0xf4000000, 0xf50fffff].
+ *
+ *	OCRAM	0x00000000+0x020000	->	0xf4000000+0x020000
+ *	IO	0x80000000+0x100000	->	0xf5000000+0x100000
+ */
+#define MXS_IO_P2V(x)	(0xf4000000 +					\
+			(((x) & 0x80000000) >> 7) +			\
+			(((x) & 0x000fffff)))
+
+#define MXS_IO_ADDRESS(x)	IOMEM(MXS_IO_P2V(x))
+
+
+/* OCOTP registers and bits */
+#define HW_OCOTP_CTRL		(0x00000000)
+#define HW_OCOTP_CTRL_SET	(0x00000004)
+#define HW_OCOTP_CTRL_CLR	(0x00000008)
+#define HW_OCOTP_CTRL_TOG	(0x0000000c)
+
+#define BM_OCOTP_CTRL_RELOAD_SHADOWS	0x00002000
+#define BM_OCOTP_CTRL_RD_BANK_OPEN	0x00001000
+#define BM_OCOTP_CTRL_ERROR		0x00000200
+#define BM_OCOTP_CTRL_BUSY		0x00000100
+#define BP_OCOTP_CTRL_ADDR		0
+#if defined(CONFIG_SOC_IMX28)
+#define BM_OCOTP_CTRL_ADDR		0x0000003F
+#endif
+#if defined(CONFIG_SOC_IMX23)
+#define BM_OCOTP_CTRL_ADDR		0x0000001F
+#endif
+#define BP_OCOTP_CTRL_WR_UNLOCK		16
+#define BM_OCOTP_CTRL_WR_UNLOCK		0xFFFF0000
+
+#define HW_OCOTP_DATA	(0x00000010)
+
+#define HW_OCOTP_CUST_N(n)	(0x00000020 + (n) * 0x10)
+#define BP_OCOTP_CUST_N_BITS	0
+#define BM_OCOTP_CUST_N_BITS	0xFFFFFFFF
+#define BF_OCOTP_CUST_N_BITS(v)	(v)
+
+
+
+#if defined(CONFIG_SOC_IMX28)
+/* Building up eight registers's names of a bank */
+#define MXS_OTP_BANK(a, b, c, d, e, f, g, h)	\
+	{\
+	("HW_OCOTP_"#a), ("HW_OCOTP_"#b), ("HW_OCOTP_"#c), ("HW_OCOTP_"#d), \
+	("HW_OCOTP_"#e), ("HW_OCOTP_"#f), ("HW_OCOTP_"#g), ("HW_OCOTP_"#h) \
+	}
+
+#define MXS_OTP_BANKS		(5)
+#define MXS_OTP_BANK_ITEMS	(8)
+static const char *bank_reg_desc[MXS_OTP_BANKS][MXS_OTP_BANK_ITEMS] = {
+MXS_OTP_BANK(CUST0, CUST1, CUST2, CUST3, CRYPTO0, CRYPTO1, CRYPTO2, CRYPTO3),
+MXS_OTP_BANK(HWCAP0, HWCAP1, HWCAP2, HWCAP3, HWCAP4, HWCAP5, SWCAP, CUSTCAP),
+MXS_OTP_BANK(LOCK, OPS0, OPS1, OPS2, OPS3, UN0, UN1, UN2),
+MXS_OTP_BANK(ROM0, ROM1, ROM2, ROM3, ROM4, ROM5, ROM6, ROM7),
+MXS_OTP_BANK(SRK0, SRK1, SRK2, SRK3, SRK4, SRK5, SRK6, SRK7),
+};
+#endif /* if defined(CONFIG_SOC_IMX28) */
+
+
+#if defined(CONFIG_SOC_IMX23)
+/* Building up eight registers's names of a bank */
+#define MXS_OTP_BANK(a, b, c, d, e, f, g, h)	\
+	{\
+	("HW_OCOTP_"#a), ("HW_OCOTP_"#b), ("HW_OCOTP_"#c), ("HW_OCOTP_"#d), \
+	("HW_OCOTP_"#e), ("HW_OCOTP_"#f), ("HW_OCOTP_"#g), ("HW_OCOTP_"#h) \
+	}
+
+#define MXS_OTP_BANKS		(4)
+#define MXS_OTP_BANK_ITEMS	(8)
+static const char *bank_reg_desc[MXS_OTP_BANKS][MXS_OTP_BANK_ITEMS] = {
+MXS_OTP_BANK(CUST0, CUST1, CUST2, CUST3, CRYPTO0, CRYPTO1, CRYPTO2, CRYPTO3),
+MXS_OTP_BANK(HWCAP0, HWCAP1, HWCAP2, HWCAP3, HWCAP4, HWCAP5, SWCAP, CUSTCAP),
+MXS_OTP_BANK(LOCK, OPS0, OPS1, OPS2, OPS3, UN0, UN1, UN2),
+MXS_OTP_BANK(ROM0, ROM1, ROM2, ROM3, ROM4, ROM5, ROM6, ROM7),
+};
+
+#endif/* if defined(CONFIG_SOC_IMX23) */
+
+struct fsl_otp_data {
+	char		**fuse_name;
+	char		*regulator_name;
+	unsigned int	fuse_num;
+};
+
+#endif /* (defined(CONFIG_SOC_IMX23) || defined(CONFIG_SOC_IMX28)) */
+#endif