Message-ID: <1303248968-5069-1-git-send-email-guenter.roeck@ericsson.com>
Date:	Tue, 19 Apr 2011 14:36:08 -0700
From:	Guenter Roeck <guenter.roeck@...csson.com>
To:	Greg Kroah-Hartman <gregkh@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Jonathan Cameron <kernel@...23.retrosnub.co.uk>,
	Randy Dunlap <rdunlap@...otime.net>,
	<linux-doc@...r.kernel.org>, <linux-i2c@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Guenter Roeck <guenter.roeck@...csson.com>
Subject: [PATCH v2] misc: Driver for Silicon Labs Si570 and compatibles

This driver adds support for Si570, Si571, Si598, and Si599
programmable XO/VCXO.

Signed-off-by: Guenter Roeck <guenter.roeck@...csson.com>
---
v2:
- Fixed checkpatch errors and warnings
- Moved si570.h platform data include file to include/linux/platform_data
- Documented reset sysfs attribute
- Added Documentation/ABI/testing/sysfs-bus-i2c-si570

 Documentation/ABI/testing/sysfs-bus-i2c-si570 |   21 ++
 Documentation/misc-devices/si570              |   62 ++++
 MAINTAINERS                                   |    7 +
 drivers/misc/Kconfig                          |   10 +
 drivers/misc/Makefile                         |    1 +
 drivers/misc/si570.c                          |  398 +++++++++++++++++++++++++
 include/linux/platform_data/si570.h           |   23 ++
 7 files changed, 522 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-i2c-si570
 create mode 100644 Documentation/misc-devices/si570
 create mode 100644 drivers/misc/si570.c
 create mode 100644 include/linux/platform_data/si570.h

diff --git a/Documentation/ABI/testing/sysfs-bus-i2c-si570 b/Documentation/ABI/testing/sysfs-bus-i2c-si570
new file mode 100644
index 0000000..78c43f7
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-i2c-si570
@@ -0,0 +1,21 @@
+What:		/sys/bus/i2c/devices/<busnum>-<devaddr>/frequency
+Date:		April 2011
+Kernel version:	2.6.40 ?
+Contact:	Guenter Roeck <guenter.roeck@...csson.com>
+Description:
+		Read or write XO/VCXO frequency of the device in Hz.
+
+		Accepted values: 10 MHz to 1400 MHz for Si570 and Si571,
+		10 MHz to 525 MHz for Si598 and Si599.
+Users:
+		Userspace applications interested in knowing or changing the
+		device frequency.
+
+What:		/sys/bus/i2c/devices/<busnum>-<devaddr>/reset
+Date:		April 2011
+Kernel Version: 2.6.40 ?
+Contact:	Guenter Roeck <guenter.roeck@...csson.com>
+Description:	Writing a value other than 0 resets the device.
+		Reading always returns 0 and has no effect.
+Users:
+		Userspace applications interested in resetting the device.
diff --git a/Documentation/misc-devices/si570 b/Documentation/misc-devices/si570
new file mode 100644
index 0000000..54e32f7
--- /dev/null
+++ b/Documentation/misc-devices/si570
@@ -0,0 +1,62 @@
+Kernel driver si570
+=====================
+
+Supported chips:
+  * Silicon Labs Si570/Si571
+    Prefix: 'si570'
+    Addresses scanned: None (see below)
+    Datasheets:
+        http://www.silabs.com/Support%20Documents/TechnicalDocs/si570.pdf
+  * Silicon Labs Si598/Si599
+    Prefix: 'si598'
+    Addresses scanned: None (see below)
+    Datasheets:
+	http://www.silabs.com/Support%20Documents/TechnicalDocs/si598-99.pdf
+
+Author: Guenter Roeck <guenter.roeck@...csson.com>
+
+
+Description
+-----------
+
+The Si570/Si598 XO and Si571/Si599 VCXO provide a low-jitter clock at any
+frequency.
+
+The Si570/Si571 are user-programmable to any output frequency from 10 to 945 MHz
+and select frequencies to 1400 MHz with <1 ppb resolution.
+
+The Si598/Si599 are user programmable to any output frequency from 10 to 525 MHz
+with 28 parts per trillion (ppt) resolution.
+
+See the datasheets for more information.
+
+
+Sysfs entries
+-------------
+
+frequency	- Selected frequency
+reset		- Writing a value other than 0 resets the device
+
+
+General Remarks
+---------------
+
+The chips support all valid 7-bit I2C addresses. I2C addresses are assigned
+during the ordering process.
+
+This driver does not auto-detect devices. You will have to instantiate the
+devices explicitly. Please see Documentation/i2c/instantiating-devices for
+details.
+
+
+Platform data
+-------------
+
+The devices can be provided with platform data to select the factory default
+output frequency. If platform data is not specified, the driver will assume a
+default factory output frequency of 125 MHz for Si570/Si571 and 10 MHz for
+Si598/Si599.
+
+struct si570_platform_data {
+	unsigned long fout;	/* Factory default output frequency */
+};
diff --git a/MAINTAINERS b/MAINTAINERS
index ec36003..4c339ea 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5406,6 +5406,13 @@ L:	linux-serial@...r.kernel.org
 S:	Maintained
 F:	drivers/tty/serial
 
+SI570 DRIVER
+M:	Guenter Roeck <guenter.roeck@...csson.com>
+L:	linux-kernel@...r.kernel.org
+S:	Maintained
+F:	drivers/misc/si570.c
+F:	include/linux/platform_data/si570.h
+
 TIMEKEEPING, NTP
 M:	John Stultz <johnstul@...ibm.com>
 M:	Thomas Gleixner <tglx@...utronix.de>
diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 4e007c6..c7041c9 100644
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -475,6 +475,16 @@ config PCH_PHUB
 	  To compile this driver as a module, choose M here: the module will
 	  be called pch_phub.
 
+config SI570
+	tristate "Silicon Labs Si570/Si571/Si598/Si599"
+	depends on I2C && SYSFS && EXPERIMENTAL
+	help
+	  This is a driver for Silicon Labs Si570/Si571/Si598/Si599 programmable
+	  XO/VCXO.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called si570.
+
 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 f546860..a2397c6 100644
--- a/drivers/misc/Makefile
+++ b/drivers/misc/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_SPEAR13XX_PCIE_GADGET)	+= spear13xx_pcie_gadget.o
 obj-$(CONFIG_VMWARE_BALLOON)	+= vmw_balloon.o
 obj-$(CONFIG_ARM_CHARLCD)	+= arm-charlcd.o
 obj-$(CONFIG_PCH_PHUB)		+= pch_phub.o
+obj-$(CONFIG_SI570)		+= si570.o
 obj-y				+= ti-st/
 obj-$(CONFIG_AB8500_PWM)	+= ab8500-pwm.o
 obj-y				+= lis3lv02d/
diff --git a/drivers/misc/si570.c b/drivers/misc/si570.c
new file mode 100644
index 0000000..69a3806
--- /dev/null
+++ b/drivers/misc/si570.c
@@ -0,0 +1,398 @@
+/*
+ * Driver for Silicon Labs Si570/Si571 Programmable XO/VCXO
+ *
+ * Copyright (C) 2011 Ericsson AB.
+ *
+ * Author: Guenter Roeck <guenter.roeck@...csson.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.
+ *
+ * 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/module.h>
+#include <linux/jiffies.h>
+#include <linux/i2c.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/delay.h>
+#include <linux/log2.h>
+#include <linux/slab.h>
+#include <linux/platform_data/si570.h>
+
+/* Si570 registers */
+#define SI570_REG_HS_N1		7
+#define SI570_REG_N1_RFREQ0	8
+#define SI570_REG_RFREQ1	9
+#define SI570_REG_RFREQ2	10
+#define SI570_REG_RFREQ3	11
+#define SI570_REG_RFREQ4	12
+#define SI570_REG_CONTROL	135
+#define SI570_REG_FREEZE_DCO	137
+
+#define HS_DIV_SHIFT		5
+#define HS_DIV_MASK		0xe0
+#define HS_DIV_OFFSET		4
+#define N1_6_2_MASK		0x1f
+#define N1_1_0_MASK		0xc0
+#define RFREQ_37_32_MASK	0x3f
+
+#define SI570_FOUT_FACTORY_DFLT	125000000LL
+#define SI598_FOUT_FACTORY_DFLT	10000000LL
+
+#define SI570_MIN_FREQ		10000000L
+#define SI570_MAX_FREQ		1417500000L
+#define SI598_MAX_FREQ		525000000L
+
+#define FDCO_MIN		4850000000LL
+#define FDCO_MAX		5670000000LL
+#define FDCO_CENTER		((FDCO_MIN + FDCO_MAX) / 2)
+
+#define SI570_CNTRL_RECALL	(1 << 0)
+#define SI570_CNTRL_FREEZE_ADC	(1 << 4)
+#define SI570_CNTRL_FREEZE_M	(1 << 5)
+#define SI570_CNTRL_NEWFREQ	(1 << 6)
+#define SI570_CNTRL_RESET	(1 << 7)
+
+#define SI570_FREEZE_DCO	(1 << 4)
+
+struct si570_data {
+	struct attribute_group attrs;
+	struct mutex lock;
+	u64 max_freq;
+	u64 fout;		/* Factory default frequency */
+	u64 fxtal;		/* Factory xtal frequency */
+	unsigned int n1;
+	unsigned int hs_div;
+	u64 rfreq;
+	u64 frequency;
+};
+
+static int si570_get_defaults(struct i2c_client *client)
+{
+	struct si570_data *data = i2c_get_clientdata(client);
+	int reg1, reg2, reg3, reg4, reg5, reg6;
+	u64 fdco;
+
+	i2c_smbus_write_byte_data(client, SI570_REG_CONTROL,
+				  SI570_CNTRL_RECALL);
+
+	reg1 = i2c_smbus_read_byte_data(client, SI570_REG_HS_N1);
+	if (reg1 < 0)
+		return reg1;
+	reg2 = i2c_smbus_read_byte_data(client, SI570_REG_N1_RFREQ0);
+	if (reg2 < 0)
+		return reg2;
+	reg3 = i2c_smbus_read_byte_data(client, SI570_REG_RFREQ1);
+	if (reg3 < 0)
+		return reg3;
+	reg4 = i2c_smbus_read_byte_data(client, SI570_REG_RFREQ2);
+	if (reg4 < 0)
+		return reg4;
+	reg5 = i2c_smbus_read_byte_data(client, SI570_REG_RFREQ3);
+	if (reg5 < 0)
+		return reg5;
+	reg6 = i2c_smbus_read_byte_data(client, SI570_REG_RFREQ4);
+	if (reg6 < 0)
+		return reg6;
+
+	data->hs_div = ((reg1 & HS_DIV_MASK) >> HS_DIV_SHIFT) + HS_DIV_OFFSET;
+	data->n1 = ((reg1 & N1_6_2_MASK) << 2) + ((reg2 & N1_1_0_MASK) >> 6)
+	  + 1;
+	/* Handle invalid cases */
+	if (data->n1 > 1)
+		data->n1 &= ~1;
+
+	data->rfreq = reg2 & RFREQ_37_32_MASK;
+	data->rfreq = (data->rfreq << 8) + reg3;
+	data->rfreq = (data->rfreq << 8) + reg4;
+	data->rfreq = (data->rfreq << 8) + reg5;
+	data->rfreq = (data->rfreq << 8) + reg6;
+
+	/*
+	 * Accept optional precision loss to avoid arithmetic overflows.
+	 * Acceptable per Silicon Labs Application Note AN334.
+	 */
+	fdco = data->fout * data->n1 * data->hs_div;
+	if (fdco >= (1LL << 36))
+		data->fxtal = (fdco << 24) / (data->rfreq >> 4);
+	else
+		data->fxtal = (fdco << 28) / data->rfreq;
+
+	data->frequency = data->fout;
+
+	return 0;
+}
+
+/*
+ * Update rfreq registers
+ * This function must be called with update mutex lock held.
+ */
+static void si570_update_rfreq(struct i2c_client *client,
+			       struct si570_data *data)
+{
+	i2c_smbus_write_byte_data(client, SI570_REG_N1_RFREQ0,
+				  ((data->n1 - 1) << 6)
+				  | ((data->rfreq >> 32) & RFREQ_37_32_MASK));
+	i2c_smbus_write_byte_data(client, SI570_REG_RFREQ1,
+				  (data->rfreq >> 24) & 0xff);
+	i2c_smbus_write_byte_data(client, SI570_REG_RFREQ2,
+				  (data->rfreq >> 16) & 0xff);
+	i2c_smbus_write_byte_data(client, SI570_REG_RFREQ3,
+				  (data->rfreq >> 8) & 0xff);
+	i2c_smbus_write_byte_data(client, SI570_REG_RFREQ4,
+				  data->rfreq & 0xff);
+}
+
+/*
+ * Update si570 frequency for small frequency changes (< 3,500 ppm)
+ * This function must be called with update mutex lock held.
+ */
+static int si570_set_frequency_small(struct i2c_client *client,
+				     struct si570_data *data,
+				     unsigned long frequency)
+{
+	data->frequency = frequency;
+	data->rfreq = DIV_ROUND_CLOSEST(data->rfreq * frequency,
+					data->frequency);
+	i2c_smbus_write_byte_data(client, SI570_REG_CONTROL,
+				  SI570_CNTRL_FREEZE_M);
+	si570_update_rfreq(client, data);
+	i2c_smbus_write_byte_data(client, SI570_REG_CONTROL, 0);
+
+	return 0;
+}
+
+const uint8_t si570_hs_div_values[] = { 11, 9, 7, 6, 5, 4 };
+
+/*
+ * Set si570 frequency.
+ * This function must be called with update mutex lock held.
+ */
+static int si570_set_frequency(struct i2c_client *client,
+			       struct si570_data *data,
+			       unsigned long frequency)
+{
+	int i, n1, hs_div;
+	u64 fdco, best_fdco = ULLONG_MAX;
+
+	for (i = 0; i < ARRAY_SIZE(si570_hs_div_values); i++) {
+		hs_div = si570_hs_div_values[i];
+		/* Calculate lowest possible value for n1 */
+		n1 = FDCO_MIN / (u64)hs_div / (u64)frequency;
+		if (!n1 || (n1 & 1))
+			n1++;
+		while (n1 <= 128) {
+			fdco = (u64)frequency * (u64)hs_div * (u64)n1;
+			if (fdco > FDCO_MAX)
+				break;
+			if (fdco >= FDCO_MIN && fdco < best_fdco) {
+				data->n1 = n1;
+				data->hs_div = hs_div;
+				data->frequency = frequency;
+				data->rfreq = (fdco << 28) / data->fxtal;
+				best_fdco = fdco;
+			}
+			n1 += (n1 == 1 ? 1 : 2);
+		}
+	}
+	if (best_fdco == ULLONG_MAX)
+		return -EINVAL;
+
+	i2c_smbus_write_byte_data(client, SI570_REG_FREEZE_DCO,
+				  SI570_FREEZE_DCO);
+	i2c_smbus_write_byte_data(client, SI570_REG_HS_N1,
+				  ((data->hs_div - HS_DIV_OFFSET) <<
+				   HS_DIV_SHIFT)
+				  | (((data->n1 - 1) >> 2) & N1_6_2_MASK));
+	si570_update_rfreq(client, data);
+	i2c_smbus_write_byte_data(client, SI570_REG_FREEZE_DCO,
+				  0);
+	i2c_smbus_write_byte_data(client, SI570_REG_CONTROL,
+				  SI570_CNTRL_NEWFREQ);
+	return 0;
+}
+
+/*
+ * Reset chip.
+ * This function must be called with update mutex lock held.
+ */
+static int si570_reset(struct i2c_client *client, struct si570_data *data)
+{
+	i2c_smbus_write_byte_data(client, SI570_REG_CONTROL,
+				  SI570_CNTRL_RESET);
+	usleep_range(1000, 5000);
+	return si570_set_frequency(client, data, data->frequency);
+}
+
+static ssize_t show_frequency(struct device *dev,
+			      struct device_attribute *devattr,
+			      char *buf)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct si570_data *data = i2c_get_clientdata(client);
+
+	return sprintf(buf, "%llu\n", data->frequency);
+}
+
+static ssize_t set_frequency(struct device *dev,
+			     struct device_attribute *attr,
+			     const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct si570_data *data = i2c_get_clientdata(client);
+	unsigned long val;
+	int err;
+
+	err = strict_strtoul(buf, 10, &val);
+	if (err)
+		return err;
+
+	if (val < SI570_MIN_FREQ || val > data->max_freq)
+		return -EINVAL;
+
+	mutex_lock(&data->lock);
+	if (abs(val - data->frequency) * 10000LL / data->frequency < 35)
+		err = si570_set_frequency_small(client, data, val);
+	else
+		err = si570_set_frequency(client, data, val);
+	mutex_unlock(&data->lock);
+	if (err)
+		return err;
+
+	return count;
+}
+static ssize_t show_reset(struct device *dev,
+			  struct device_attribute *devattr,
+			  char *buf)
+{
+	return sprintf(buf, "%d\n", 0);
+}
+
+static ssize_t set_reset(struct device *dev,
+			 struct device_attribute *attr,
+			 const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct si570_data *data = i2c_get_clientdata(client);
+	unsigned long val;
+	int err;
+
+	err = strict_strtoul(buf, 10, &val);
+	if (err)
+		return err;
+	if (val == 0)
+		goto done;
+
+	mutex_lock(&data->lock);
+	err = si570_reset(client, data);
+	mutex_unlock(&data->lock);
+	if (err)
+		return err;
+done:
+	return count;
+}
+
+static DEVICE_ATTR(frequency, S_IWUSR | S_IRUGO, show_frequency, set_frequency);
+static DEVICE_ATTR(reset, S_IWUSR | S_IRUGO, show_reset, set_reset);
+
+static struct attribute *si570_attr[] = {
+	&dev_attr_frequency.attr,
+	&dev_attr_reset.attr,
+	NULL
+};
+
+static const struct i2c_device_id si570_id[] = {
+	{ "si570", 0 },
+	{ "si571", 0 },
+	{ "si598", 1 },
+	{ "si599", 1 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, si570_id);
+
+static int si570_probe(struct i2c_client *client,
+		       const struct i2c_device_id *id)
+{
+	struct si570_platform_data *pdata = client->dev.platform_data;
+	struct si570_data *data;
+	int err;
+
+	data = kzalloc(sizeof(struct si570_data), GFP_KERNEL);
+	if (!data) {
+		err = -ENOMEM;
+		goto exit;
+	}
+
+	if (id->driver_data) {
+		data->fout = SI598_FOUT_FACTORY_DFLT;
+		data->max_freq = SI598_MAX_FREQ;
+	} else {
+		data->fout = SI570_FOUT_FACTORY_DFLT;
+		data->max_freq = SI570_MAX_FREQ;
+	}
+
+	if (pdata && pdata->fout)
+		data->fout = pdata->fout;
+
+	i2c_set_clientdata(client, data);
+	err = si570_get_defaults(client);
+	if (err < 0)
+		goto exit_free;
+
+	mutex_init(&data->lock);
+
+	/* Register sysfs hooks */
+	data->attrs.attrs = si570_attr;
+	err = sysfs_create_group(&client->dev.kobj, &data->attrs);
+	if (err)
+		goto exit_free;
+
+	return 0;
+
+exit_free:
+	kfree(data);
+exit:
+	return err;
+}
+
+static int si570_remove(struct i2c_client *client)
+{
+	struct si570_data *data = i2c_get_clientdata(client);
+
+	sysfs_remove_group(&client->dev.kobj, &data->attrs);
+	kfree(data);
+	return 0;
+}
+
+static struct i2c_driver si570_driver = {
+	.driver = {
+		.name	= "si570",
+	},
+	.probe		= si570_probe,
+	.remove		= si570_remove,
+	.id_table	= si570_id,
+};
+
+static int __init si570_init(void)
+{
+	return i2c_add_driver(&si570_driver);
+}
+
+static void __exit si570_exit(void)
+{
+	i2c_del_driver(&si570_driver);
+}
+
+MODULE_AUTHOR("Guenter Roeck <guenter.roeck@...csson.com>");
+MODULE_DESCRIPTION("Si570 driver");
+MODULE_LICENSE("GPL");
+
+module_init(si570_init);
+module_exit(si570_exit);
diff --git a/include/linux/platform_data/si570.h b/include/linux/platform_data/si570.h
new file mode 100644
index 0000000..22ec865
--- /dev/null
+++ b/include/linux/platform_data/si570.h
@@ -0,0 +1,23 @@
+/*
+ * si570.h - Configuration for si570 misc driver.
+ *
+ * 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 (version 2 of the License only).
+ *
+ * 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_SI570_H
+#define __LINUX_SI570_H
+
+#include <linux/types.h>
+
+struct si570_platform_data {
+	unsigned long fout;	/* Factory default output frequency */
+};
+
+#endif /* __LINUX_SI570_H */
-- 
1.7.3.1

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