mfd: Add basic WM831x OTP support

The WM831x series of devices use OTP (One Time Programmable, a type
of PROM) to store system configuration. At run time this data is
visible via registers.

Currently the only explicitly supported feature is that the unique
ID provided by every WM831x device is exported to user space via
sysfs. Other configuration data may be read by system-specific
code in the pre_init() and post_init() platform data operations.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/wm831x-core.c

@@ -23,6 +23,7 @@
 #include <linux/mfd/wm831x/pdata.h>
 #include <linux/mfd/wm831x/irq.h>
 #include <linux/mfd/wm831x/auxadc.h>
+#include <linux/mfd/wm831x/otp.h>
 
 enum wm831x_parent {
 	WM8310 = 0,
@@ -1340,6 +1341,8 @@ static int wm831x_device_init(struct wm831x *wm831x, unsigned long id, int irq)
 				ret);
 	}
 
+	wm831x_otp_init(wm831x);
+
 	if (pdata && pdata->post_init) {
 		ret = pdata->post_init(wm831x);
 		if (ret != 0) {
@@ -1360,6 +1363,7 @@ err:
 
 static void wm831x_device_exit(struct wm831x *wm831x)
 {
+	wm831x_otp_exit(wm831x);
 	mfd_remove_devices(wm831x->dev);
 	wm831x_irq_exit(wm831x);
 	kfree(wm831x);

drivers/mfd/wm831x-otp.c

@@ -0,0 +1,83 @@
+/*
+ * wm831x-otp.c  --  OTP for Wolfson WM831x PMICs
+ *
+ * Copyright 2009 Wolfson Microelectronics PLC.
+ *
+ * Author: Mark Brown <broonie@opensource.wolfsonmicro.com>
+ *
+ *  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.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/i2c.h>
+#include <linux/bcd.h>
+#include <linux/delay.h>
+#include <linux/mfd/core.h>
+
+#include <linux/mfd/wm831x/core.h>
+#include <linux/mfd/wm831x/otp.h>
+
+/* In bytes */
+#define WM831X_UNIQUE_ID_LEN 16
+
+/* Read the unique ID from the chip into id */
+static int wm831x_unique_id_read(struct wm831x *wm831x, char *id)
+{
+	int i, val;
+
+	for (i = 0; i < WM831X_UNIQUE_ID_LEN / 2; i++) {
+		val = wm831x_reg_read(wm831x, WM831X_UNIQUE_ID_1 + i);
+		if (val < 0)
+			return val;
+
+		id[i * 2]       = (val >> 8) & 0xff;
+		id[(i * 2) + 1] = val & 0xff;
+	}
+
+	return 0;
+}
+
+static ssize_t wm831x_unique_id_show(struct device *dev,
+				     struct device_attribute *attr, char *buf)
+{
+	struct wm831x *wm831x = dev_get_drvdata(dev);
+	int i, rval;
+	char id[WM831X_UNIQUE_ID_LEN];
+	ssize_t ret = 0;
+
+	rval = wm831x_unique_id_read(wm831x, id);
+	if (rval < 0)
+		return 0;
+
+	for (i = 0; i < WM831X_UNIQUE_ID_LEN; i++)
+		ret += sprintf(&buf[ret], "%02x", buf[i]);
+
+	ret += sprintf(&buf[ret], "\n");
+
+	return ret;
+}
+
+static DEVICE_ATTR(unique_id, 0444, wm831x_unique_id_show, NULL);
+
+int wm831x_otp_init(struct wm831x *wm831x)
+{
+	int ret;
+
+	ret = device_create_file(wm831x->dev, &dev_attr_unique_id);
+	if (ret != 0)
+		dev_err(wm831x->dev, "Unique ID attribute not created: %d\n",
+			ret);
+
+	return ret;
+}
+
+void wm831x_otp_exit(struct wm831x *wm831x)
+{
+	device_remove_file(wm831x->dev, &dev_attr_unique_id);
+}
+