Date:	Wed, 19 Aug 2009 01:29:19 +0200
From:	Samuel Ortiz <sameo@...ux.intel.com>
To:	Linus Walleij <linus.walleij@...ricsson.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MFD AB3100 OTP readout v2

Hi Linus,

On Tue, Aug 18, 2009 at 10:52:26PM +0200, Linus Walleij wrote:
> This adds the ability to read out OTP (One-Time Programmable)
> registers in the AB3100 MFD ASIC. It's a simple sysfs file you
> can cat to prompt. The OTP registers of the AB3100 are used to
> store various device-unique information such as customer ID,
> product flags and the 3GPP standard IMEI (International Mobile
> Equipment Indentity) number.
> 
> Signed-off-by: Linus Walleij <linus.walleij@...ricsson.com>
> Reviewed-by: Samuel Ortiz <sameo@...ux.intel.com>
> ---
> ChangeLog v1->v2:
> - added Kconfig entry making all OTP support optional and
>   thus it also makes more sense to have it as a subdevice
>   in a single, separate .c file.
I still dont get why you want that to be a device by its own.
I'm OK with a Kconfig entry although I dont see how adding 8 sysfs entries
could hurt, but a platform driver for it really seems an overkill to me. Do
you have a good reason that I'd be currently missing ?
Having a no-op for ab3100_otp_probe() when AB3100_OTP is not defined would be
a lighter solution, wouldn't it ?

Cheers,
Samuel.


> - added a local state holder for the driver instead of
>   reading out these values causing I2C traffic for no
>   good reason as they cannot change anyway.
> - move all properties over to one value per file sysfs
>   entries.
> - moved the human-readable file with summary to debugfs
>   and only compile it in if debugfs was selected.
> ---
>  drivers/mfd/Kconfig      |    9 ++
>  drivers/mfd/Makefile     |    1 +
>  drivers/mfd/ab3100-otp.c |  268 ++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 278 insertions(+), 0 deletions(-)
>  create mode 100644 drivers/mfd/ab3100-otp.c
> 
> diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
> index 491ac0f..fc3eab5 100644
> --- a/drivers/mfd/Kconfig
> +++ b/drivers/mfd/Kconfig
> @@ -256,6 +256,15 @@ config AB3100_CORE
>  	  LEDs, vibrator, system power and temperature, power management
>  	  and ALSA sound.
>  
> +config AB3100_OTP
> +	tristate "ST-Ericsson AB3100 OTP functions"
> +	depends on AB3100_CORE
> +	default y if AB3100_CORE
> +	help
> +	  Select this to enable the AB3100 Mixed Signal IC OTP (one-time
> +	  programmable memory) support. This exposes a sysfs file to read
> +	  out OTP values.
> +
>  config EZX_PCAP
>  	bool "PCAP Support"
>  	depends on GENERIC_HARDIRQS && SPI_MASTER
> diff --git a/drivers/mfd/Makefile b/drivers/mfd/Makefile
> index 6f8a9a1..b61e5c9 100644
> --- a/drivers/mfd/Makefile
> +++ b/drivers/mfd/Makefile
> @@ -44,3 +44,4 @@ obj-$(CONFIG_MFD_PCF50633)	+= pcf50633-core.o
>  obj-$(CONFIG_PCF50633_ADC)	+= pcf50633-adc.o
>  obj-$(CONFIG_PCF50633_GPIO)	+= pcf50633-gpio.o
>  obj-$(CONFIG_AB3100_CORE)	+= ab3100-core.o
> +obj-$(CONFIG_AB3100_OTP)	+= ab3100-otp.o
> diff --git a/drivers/mfd/ab3100-otp.c b/drivers/mfd/ab3100-otp.c
> new file mode 100644
> index 0000000..0499b20
> --- /dev/null
> +++ b/drivers/mfd/ab3100-otp.c
> @@ -0,0 +1,268 @@
> +/*
> + * drivers/mfd/ab3100_otp.c
> + *
> + * Copyright (C) 2007-2009 ST-Ericsson AB
> + * License terms: GNU General Public License (GPL) version 2
> + * Driver to read out OTP from the AB3100 Mixed-signal circuit
> + * Author: Linus Walleij <linus.walleij@...ricsson.com>
> + */
> +
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/init.h>
> +#include <linux/platform_device.h>
> +#include <linux/mfd/ab3100.h>
> +#include <linux/debugfs.h>
> +
> +/* The OTP registers */
> +#define AB3100_OTP0		0xb0
> +#define AB3100_OTP1		0xb1
> +#define AB3100_OTP2		0xb2
> +#define AB3100_OTP3		0xb3
> +#define AB3100_OTP4		0xb4
> +#define AB3100_OTP5		0xb5
> +#define AB3100_OTP6		0xb6
> +#define AB3100_OTP7		0xb7
> +#define AB3100_OTPP		0xbf
> +
> +/**
> + * struct ab3100_otp
> + * @dev containing device
> + * @ab3100 a pointer to the parent ab3100 device struct
> + * @locked whether the OTP is locked, after locking, no more bits
> + *       can be changed but before locking it is still possible
> + *       to change bits from 1->0.
> + * @freq clocking frequency for the OTP, this frequency is either
> + *       32768Hz or 1MHz/30
> + * @paf product activation flag, indicates whether this is a real
> + *       product (paf true) or a lab board etc (paf false)
> + * @imeich if this is set it is possible to override the
> + *       IMEI number found in the tac, fac and svn fields with
> + *       (secured) software
> + * @cid customer ID
> + * @tac type allocation code of the IMEI
> + * @fac final assembly code of the IMEI
> + * @svn software version number of the IMEI
> + * @debugfs a debugfs file used when dumping to file
> + */
> +struct ab3100_otp {
> +	struct device *dev;
> +	struct ab3100 *ab3100;
> +	bool locked;
> +	u32 freq;
> +	bool paf;
> +	bool imeich;
> +	u16 cid:14;
> +	u32 tac:20;
> +	u8 fac;
> +	u32 svn:20;
> +	struct dentry *debugfs;
> +};
> +
> +static int __init ab3100_otp_read(struct ab3100_otp *otp)
> +{
> +	struct ab3100 *ab = otp->ab3100;
> +	u8 otpval[8];
> +	u8 otpp;
> +	int err;
> +
> +	err = ab3100_get_register_interruptible(ab, AB3100_OTPP, &otpp);
> +	if (err) {
> +		dev_err(otp->dev, "unable to read OTPP register\n");
> +		return err;
> +	}
> +
> +	err = ab3100_get_register_page_interruptible(ab, AB3100_OTP0,
> +						     otpval, 8);
> +	if (err) {
> +		dev_err(otp->dev, "unable to read OTP register page\n");
> +		return err;
> +	}
> +
> +	/* Cache OTP properties, they never change by nature */
> +	otp->locked = (otpp & 0x80);
> +	otp->freq = (otpp & 0x40) ? 32768 : 34100;
> +	otp->paf = (otpval[1] & 0x80);
> +	otp->imeich = (otpval[1] & 0x40);
> +	otp->cid = ((otpval[1] << 8) | otpval[0]) & 0x3fff;
> +	otp->tac = ((otpval[4] & 0x0f) << 16) | (otpval[3] << 8) | otpval[2];
> +	otp->fac = ((otpval[5] & 0x0f) << 4) | (otpval[4] >> 4);
> +	otp->svn = (otpval[7] << 12) | (otpval[6] << 4) | (otpval[5] >> 4);
> +	return 0;
> +}
> +
> +/*
> + * This is a simple debugfs human-readable file that dumps out
> + * the contents of the OTP.
> + */
> +#ifdef CONFIG_DEBUGFS
> +static int show_otp(struct seq_file *s, void *v)
> +{
> +	struct ab3100_otp *otp = s->private;
> +	int err;
> +
> +	seq_printf(s, "OTP is %s\n", otp->locked ? "LOCKED" : "UNLOCKED");
> +	seq_printf(s, "OTP clock switch startup is %uHz\n", otp->freq);
> +	seq_printf(s, "PAF is %s\n", otp->paf ? "SET" : "NOT SET");
> +	seq_printf(s, "IMEI is %s\n", otp->imeich ?
> +		   "CHANGEABLE" : "NOT CHANGEABLE");
> +	seq_printf(s, "CID: 0x%04x (decimal: %d)\n", otp->cid, otp->cid);
> +	seq_printf(s, "IMEI: %u-%u-%u\n", otp->tac, otp->fac, otp->svn);
> +	return 0;
> +}
> +
> +static int ab3100_otp_open(struct inode *inode, struct file *file)
> +{
> +	return single_open(file, ab3100_otp_show, inode->i_private);
> +}
> +
> +static const struct file_operations ab3100_otp_operations = {
> +	.open		= ab3100_otp_open,
> +	.read		= seq_read,
> +	.llseek		= seq_lseek,
> +	.release	= single_release,
> +};
> +
> +static int __init ab3100_otp_init_debugfs(struct device *dev,
> +					  struct ab3100_otp *otp)
> +{
> +	otp->debugfs = debugfs_create_file("ab3100_otp", S_IFREG | S_IRUGO,
> +					   NULL, otp,
> +					   &ab3100_otp_operations);
> +	if (!otp->debugfs) {
> +		dev_err(dev, "AB3100 debugfs OTP file registration failed!\n");
> +		return err;
> +	}
> +}
> +
> +static void __exit ab3100_otp_exit_debugfs(struct ab3100_otp *otp)
> +{
> +	debugfs_remove_file(otp->debugfs);
> +}
> +#else
> +/* Compile this out if debugfs not selected */
> +static inline int __init ab3100_otp_init_debugfs(struct device *dev,
> +						 struct ab3100_otp *otp)
> +{
> +	return 0;
> +}
> +
> +static inline void __exit ab3100_otp_exit_debugfs(struct ab3100_otp *otp)
> +{
> +}
> +#endif
> +
> +#define SHOW_AB3100_ATTR(name) \
> +static ssize_t ab3100_otp_##name##_show(struct device *dev, \
> +			       struct device_attribute *attr, \
> +			       char *buf) \
> +{\
> +	struct ab3100_otp *otp = dev_get_drvdata(dev); \
> +	return sprintf(buf, "%u\n", otp->name); \
> +}
> +
> +SHOW_AB3100_ATTR(locked)
> +SHOW_AB3100_ATTR(freq)
> +SHOW_AB3100_ATTR(paf)
> +SHOW_AB3100_ATTR(imeich)
> +SHOW_AB3100_ATTR(cid)
> +SHOW_AB3100_ATTR(fac)
> +SHOW_AB3100_ATTR(tac)
> +SHOW_AB3100_ATTR(svn)
> +
> +static struct device_attribute ab3100_otp_attrs[] = {
> +	__ATTR(locked, S_IRUGO, ab3100_otp_locked_show, NULL),
> +	__ATTR(freq, S_IRUGO, ab3100_otp_freq_show, NULL),
> +	__ATTR(paf, S_IRUGO, ab3100_otp_paf_show, NULL),
> +	__ATTR(imeich, S_IRUGO, ab3100_otp_imeich_show, NULL),
> +	__ATTR(cid, S_IRUGO, ab3100_otp_cid_show, NULL),
> +	__ATTR(fac, S_IRUGO, ab3100_otp_fac_show, NULL),
> +	__ATTR(tac, S_IRUGO, ab3100_otp_tac_show, NULL),
> +	__ATTR(svn, S_IRUGO, ab3100_otp_svn_show, NULL),
> +};
> +
> +static int __init ab3100_otp_probe(struct platform_device *pdev)
> +{
> +	struct ab3100_otp *otp;
> +	int err = 0;
> +	int i;
> +
> +	otp = kzalloc(sizeof(struct ab3100_otp), GFP_KERNEL);
> +	if (!otp) {
> +		dev_err(&pdev->dev, "could not allocate AB3100 OTP device\n");
> +		return -ENOMEM;
> +	}
> +	otp->dev = &pdev->dev;
> +
> +	/* Replace platform data coming in with a local struct */
> +	otp->ab3100 = platform_get_drvdata(pdev);
> +	platform_set_drvdata(pdev, otp);
> +
> +	err = ab3100_otp_read(otp);
> +	if (err)
> +		return err;
> +
> +	dev_info(&pdev->dev, "AB3100 OTP readout registered\n");
> +
> +	/* sysfs entries */
> +	for (i = 0; i < ARRAY_SIZE(ab3100_otp_attrs); i++) {
> +		err = device_create_file(&pdev->dev,
> +					 &ab3100_otp_attrs[i]);
> +		if (err)
> +			goto out_no_sysfs;
> +	}
> +
> +	/* debugfs entries */
> +	err = ab3100_otp_init_debugfs(&pdev->dev, otp);
> +	if (err)
> +		goto out_no_debugfs;
> +
> +	return 0;
> +
> +out_no_sysfs:
> +	for (i = 0; i < ARRAY_SIZE(ab3100_otp_attrs); i++)
> +		device_remove_file(&pdev->dev,
> +				   &ab3100_otp_attrs[i]);
> +out_no_debugfs:
> +	kfree(otp);
> +	return err;
> +}
> +
> +static int __exit ab3100_otp_remove(struct platform_device *pdev)
> +{
> +	struct ab3100_otp *otp = platform_get_drvdata(pdev);
> +	int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(ab3100_otp_attrs); i++)
> +		device_remove_file(&pdev->dev,
> +				   &ab3100_otp_attrs[i]);
> +	ab3100_otp_exit_debugfs(otp);
> +	kfree(otp);
> +	return 0;
> +}
> +
> +static struct platform_driver ab3100_otp_driver = {
> +	.driver = {
> +		.name = "ab3100-otp",
> +		.owner = THIS_MODULE,
> +	},
> +	.remove	 = __exit_p(ab3100_otp_remove),
> +};
> +
> +static int __init ab3100_otp_init(void)
> +{
> +	return platform_driver_probe(&ab3100_otp_driver,
> +				     ab3100_otp_probe);
> +}
> +
> +static void __exit ab3100_otp_exit(void)
> +{
> +	platform_driver_unregister(&ab3100_otp_driver);
> +}
> +
> +module_init(ab3100_otp_init);
> +module_exit(ab3100_otp_exit);
> +
> +MODULE_AUTHOR("Linus Walleij <linus.walleij@...ricsson.com>");
> +MODULE_DESCRIPTION("AB3100 OTP Readout Driver");
> +MODULE_LICENSE("GPL");
> -- 
> 1.6.2.1
> 

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