[net-next-2.6.git] / drivers / rtc / rtc-dm355evm.c

/*
 * rtc-dm355evm.c - access battery-backed counter in MSP430 firmware
 *
 * Copyright (c) 2008 by David Brownell
 *
 * 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/init.h>
#include <linux/rtc.h>
#include <linux/platform_device.h>

#include <linux/i2c/dm355evm_msp.h>


/*
 * The MSP430 firmware on the DM355 EVM uses a watch crystal to feed
 * a 1 Hz counter.  When a backup battery is supplied, that makes a
 * reasonable RTC for applications where alarms and non-NTP drift
 * compensation aren't important.
 *
 * The only real glitch is the inability to read or write all four
 * counter bytes atomically:  the count may increment in the middle
 * of an operation, causing trouble when the LSB rolls over.
 *
 * This driver was tested with firmware revision A4.
 */
union evm_time {
	u8	bytes[4];
	u32	value;
};

static int dm355evm_rtc_read_time(struct device *dev, struct rtc_time *tm)
{
	union evm_time	time;
	int		status;
	int		tries = 0;

	do {
		/*
		 * Read LSB(0) to MSB(3) bytes.  Defend against the counter
		 * rolling over by re-reading until the value is stable,
		 * and assuming the four reads take at most a few seconds.
		 */
		status = dm355evm_msp_read(DM355EVM_MSP_RTC_0);
		if (status < 0)
			return status;
		if (tries && time.bytes[0] == status)
			break;
		time.bytes[0] = status;

		status = dm355evm_msp_read(DM355EVM_MSP_RTC_1);
		if (status < 0)
			return status;
		if (tries && time.bytes[1] == status)
			break;
		time.bytes[1] = status;

		status = dm355evm_msp_read(DM355EVM_MSP_RTC_2);
		if (status < 0)
			return status;
		if (tries && time.bytes[2] == status)
			break;
		time.bytes[2] = status;

		status = dm355evm_msp_read(DM355EVM_MSP_RTC_3);
		if (status < 0)
			return status;
		if (tries && time.bytes[3] == status)
			break;
		time.bytes[3] = status;

	} while (++tries < 5);

	dev_dbg(dev, "read timestamp %08x\n", time.value);

	rtc_time_to_tm(le32_to_cpu(time.value), tm);
	return 0;
}

static int dm355evm_rtc_set_time(struct device *dev, struct rtc_time *tm)
{
	union evm_time	time;
	unsigned long	value;
	int		status;

	rtc_tm_to_time(tm, &value);
	time.value = cpu_to_le32(value);

	dev_dbg(dev, "write timestamp %08x\n", time.value);

	/*
	 * REVISIT handle non-atomic writes ... maybe just retry until
	 * byte[1] sticks (no rollover)?
	 */
	status = dm355evm_msp_write(time.bytes[0], DM355EVM_MSP_RTC_0);
	if (status < 0)
		return status;

	status = dm355evm_msp_write(time.bytes[1], DM355EVM_MSP_RTC_1);
	if (status < 0)
		return status;

	status = dm355evm_msp_write(time.bytes[2], DM355EVM_MSP_RTC_2);
	if (status < 0)
		return status;

	status = dm355evm_msp_write(time.bytes[3], DM355EVM_MSP_RTC_3);
	if (status < 0)
		return status;

	return 0;
}

static struct rtc_class_ops dm355evm_rtc_ops = {
	.read_time	= dm355evm_rtc_read_time,
	.set_time	= dm355evm_rtc_set_time,
};

/*----------------------------------------------------------------------*/

static int __devinit dm355evm_rtc_probe(struct platform_device *pdev)
{
	struct rtc_device *rtc;

	rtc = rtc_device_register(pdev->name,
				  &pdev->dev, &dm355evm_rtc_ops, THIS_MODULE);
	if (IS_ERR(rtc)) {
		dev_err(&pdev->dev, "can't register RTC device, err %ld\n",
			PTR_ERR(rtc));
		return PTR_ERR(rtc);
	}
	platform_set_drvdata(pdev, rtc);

	return 0;
}

static int __devexit dm355evm_rtc_remove(struct platform_device *pdev)
{
	struct rtc_device *rtc = platform_get_drvdata(pdev);

	rtc_device_unregister(rtc);
	platform_set_drvdata(pdev, NULL);
	return 0;
}

/*
 * I2C is used to talk to the MSP430, but this platform device is
 * exposed by an MFD driver that manages I2C communications.
 */
static struct platform_driver rtc_dm355evm_driver = {
	.probe		= dm355evm_rtc_probe,
	.remove		= __devexit_p(dm355evm_rtc_remove),
	.driver		= {
		.owner	= THIS_MODULE,
		.name	= "rtc-dm355evm",
	},
};

static int __init dm355evm_rtc_init(void)
{
	return platform_driver_register(&rtc_dm355evm_driver);
}
module_init(dm355evm_rtc_init);

static void __exit dm355evm_rtc_exit(void)
{
	platform_driver_unregister(&rtc_dm355evm_driver);
}
module_exit(dm355evm_rtc_exit);

MODULE_LICENSE("GPL");
Commit	Line	Data
afd8d0f9 DB	1	/*
	2	* rtc-dm355evm.c - access battery-backed counter in MSP430 firmware
	3	*
	4	* Copyright (c) 2008 by David Brownell
	5	*
	6	* This program is free software; you can redistribute it and/or
	7	* modify it under the terms of the GNU General Public License
	8	* as published by the Free Software Foundation; either version
	9	* 2 of the License, or (at your option) any later version.
	10	*/
	11	#include <linux/kernel.h>
	12	#include <linux/init.h>
	13	#include <linux/rtc.h>
	14	#include <linux/platform_device.h>
	15
	16	#include <linux/i2c/dm355evm_msp.h>
	17
	18
	19	/*
	20	* The MSP430 firmware on the DM355 EVM uses a watch crystal to feed
	21	* a 1 Hz counter. When a backup battery is supplied, that makes a
	22	* reasonable RTC for applications where alarms and non-NTP drift
	23	* compensation aren't important.
	24	*
	25	* The only real glitch is the inability to read or write all four
	26	* counter bytes atomically: the count may increment in the middle
	27	* of an operation, causing trouble when the LSB rolls over.
	28	*
	29	* This driver was tested with firmware revision A4.
	30	*/
	31	union evm_time {
	32	u8 bytes[4];
	33	u32 value;
	34	};
	35
	36	static int dm355evm_rtc_read_time(struct device dev, struct rtc_time tm)
	37	{
	38	union evm_time time;
	39	int status;
	40	int tries = 0;
	41
	42	do {
	43	/*
	44	* Read LSB(0) to MSB(3) bytes. Defend against the counter
	45	* rolling over by re-reading until the value is stable,
	46	* and assuming the four reads take at most a few seconds.
	47	*/
	48	status = dm355evm_msp_read(DM355EVM_MSP_RTC_0);
	49	if (status < 0)
	50	return status;
	51	if (tries && time.bytes[0] == status)
	52	break;
	53	time.bytes[0] = status;
	54
	55	status = dm355evm_msp_read(DM355EVM_MSP_RTC_1);
	56	if (status < 0)
	57	return status;
	58	if (tries && time.bytes[1] == status)
	59	break;
	60	time.bytes[1] = status;
	61
	62	status = dm355evm_msp_read(DM355EVM_MSP_RTC_2);
	63	if (status < 0)
	64	return status;
65	if (tries && time.bytes[2] == status)
66	break;
67	time.bytes[2] = status;
68
69	status = dm355evm_msp_read(DM355EVM_MSP_RTC_3);
70	if (status < 0)
71	return status;
72	if (tries && time.bytes[3] == status)
73	break;
74	time.bytes[3] = status;
75
76	} while (++tries < 5);
77
78	dev_dbg(dev, "read timestamp %08x\n", time.value);
79
80	rtc_time_to_tm(le32_to_cpu(time.value), tm);
81	return 0;
82	}
83
84	static int dm355evm_rtc_set_time(struct device dev, struct rtc_time tm)
85	{
86	union evm_time time;
87	unsigned long value;
88	int status;
89
90	rtc_tm_to_time(tm, &value);
91	time.value = cpu_to_le32(value);
92
93	dev_dbg(dev, "write timestamp %08x\n", time.value);
94
95	/*
96	* REVISIT handle non-atomic writes ... maybe just retry until
97	* byte[1] sticks (no rollover)?
98	*/
99	status = dm355evm_msp_write(time.bytes[0], DM355EVM_MSP_RTC_0);
100	if (status < 0)
101	return status;
102
103	status = dm355evm_msp_write(time.bytes[1], DM355EVM_MSP_RTC_1);
104	if (status < 0)
105	return status;
106
107	status = dm355evm_msp_write(time.bytes[2], DM355EVM_MSP_RTC_2);
108	if (status < 0)
109	return status;
110
111	status = dm355evm_msp_write(time.bytes[3], DM355EVM_MSP_RTC_3);
112	if (status < 0)
113	return status;
114
115	return 0;
116	}
117
118	static struct rtc_class_ops dm355evm_rtc_ops = {
119	.read_time = dm355evm_rtc_read_time,
120	.set_time = dm355evm_rtc_set_time,
121	};
122
123	/----------------------------------------------------------------------/
124
125	static int __devinit dm355evm_rtc_probe(struct platform_device *pdev)
126	{
127	struct rtc_device *rtc;
128
129	rtc = rtc_device_register(pdev->name,
130	&pdev->dev, &dm355evm_rtc_ops, THIS_MODULE);
131	if (IS_ERR(rtc)) {
132	dev_err(&pdev->dev, "can't register RTC device, err %ld\n",
133	PTR_ERR(rtc));
134	return PTR_ERR(rtc);
135	}
136	platform_set_drvdata(pdev, rtc);
137
138	return 0;
139	}
140
141	static int __devexit dm355evm_rtc_remove(struct platform_device *pdev)
142	{
143	struct rtc_device *rtc = platform_get_drvdata(pdev);
144
145	rtc_device_unregister(rtc);
146	platform_set_drvdata(pdev, NULL);
147	return 0;
148	}
149
150	/*
151	* I2C is used to talk to the MSP430, but this platform device is
152	* exposed by an MFD driver that manages I2C communications.
153	*/
154	static struct platform_driver rtc_dm355evm_driver = {
155	.probe = dm355evm_rtc_probe,
156	.remove = __devexit_p(dm355evm_rtc_remove),
157	.driver = {
158	.owner = THIS_MODULE,
159	.name = "rtc-dm355evm",
160	},
161	};
162
163	static int __init dm355evm_rtc_init(void)
164	{
165	return platform_driver_register(&rtc_dm355evm_driver);
166	}
167	module_init(dm355evm_rtc_init);
168
169	static void __exit dm355evm_rtc_exit(void)
170	{
171	platform_driver_unregister(&rtc_dm355evm_driver);
172	}
173	module_exit(dm355evm_rtc_exit);
174
175	MODULE_LICENSE("GPL");