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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-02-04 18:12:01 -0500
committerLinus Torvalds <torvalds@linux-foundation.org>2009-02-05 15:56:46 -0500
commitafd8d0f940ba5078f38e435440089117ac7d9eb4 (patch)
tree1f494035691b04175ed21ed3703593ce37957925
parent77a592655cdb8d838b85fd7ecf8f36fd2870abfc (diff)
rtc: rtc-dm355evm driver
Simple RTC driver for the MSP430 firmware on the DM355 EVM board. Other than not supporting atomic reads/writes of all four bytes, this is reasonable as a basic no-alarm RTC. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com> Acked-by: Alessandro Zummo <a.zummo@towertech.it> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--drivers/rtc/Kconfig6
-rw-r--r--drivers/rtc/Makefile1
-rw-r--r--drivers/rtc/rtc-dm355evm.c175
3 files changed, 182 insertions, 0 deletions
diff --git a/drivers/rtc/Kconfig b/drivers/rtc/Kconfig
index cced4d108319..81450fbd8b12 100644
--- a/drivers/rtc/Kconfig
+++ b/drivers/rtc/Kconfig
@@ -241,6 +241,12 @@ config RTC_DRV_M41T80_WDT
241 If you say Y here you will get support for the 241 If you say Y here you will get support for the
242 watchdog timer in the ST M41T60 and M41T80 RTC chips series. 242 watchdog timer in the ST M41T60 and M41T80 RTC chips series.
243 243
244config RTC_DRV_DM355EVM
245 tristate "TI DaVinci DM355 EVM RTC"
246 depends on MFD_DM355EVM_MSP
247 help
248 Supports the RTC firmware in the MSP430 on the DM355 EVM.
249
244config RTC_DRV_TWL92330 250config RTC_DRV_TWL92330
245 boolean "TI TWL92330/Menelaus" 251 boolean "TI TWL92330/Menelaus"
246 depends on MENELAUS 252 depends on MENELAUS
diff --git a/drivers/rtc/Makefile b/drivers/rtc/Makefile
index 6e28021abb9d..0e697aa51caa 100644
--- a/drivers/rtc/Makefile
+++ b/drivers/rtc/Makefile
@@ -23,6 +23,7 @@ obj-$(CONFIG_RTC_DRV_AT91SAM9) += rtc-at91sam9.o
23obj-$(CONFIG_RTC_DRV_AU1XXX) += rtc-au1xxx.o 23obj-$(CONFIG_RTC_DRV_AU1XXX) += rtc-au1xxx.o
24obj-$(CONFIG_RTC_DRV_BFIN) += rtc-bfin.o 24obj-$(CONFIG_RTC_DRV_BFIN) += rtc-bfin.o
25obj-$(CONFIG_RTC_DRV_CMOS) += rtc-cmos.o 25obj-$(CONFIG_RTC_DRV_CMOS) += rtc-cmos.o
26obj-$(CONFIG_RTC_DRV_DM355EVM) += rtc-dm355evm.o
26obj-$(CONFIG_RTC_DRV_DS1216) += rtc-ds1216.o 27obj-$(CONFIG_RTC_DRV_DS1216) += rtc-ds1216.o
27obj-$(CONFIG_RTC_DRV_DS1286) += rtc-ds1286.o 28obj-$(CONFIG_RTC_DRV_DS1286) += rtc-ds1286.o
28obj-$(CONFIG_RTC_DRV_DS1302) += rtc-ds1302.o 29obj-$(CONFIG_RTC_DRV_DS1302) += rtc-ds1302.o
diff --git a/drivers/rtc/rtc-dm355evm.c b/drivers/rtc/rtc-dm355evm.c
new file mode 100644
index 000000000000..58d4e18530da
--- /dev/null
+++ b/drivers/rtc/rtc-dm355evm.c
@@ -0,0 +1,175 @@
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 */
31union evm_time {
32 u8 bytes[4];
33 u32 value;
34};
35
36static 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
84static 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
118static 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
125static 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
141static 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 */
154static 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
163static int __init dm355evm_rtc_init(void)
164{
165 return platform_driver_register(&rtc_dm355evm_driver);
166}
167module_init(dm355evm_rtc_init);
168
169static void __exit dm355evm_rtc_exit(void)
170{
171 platform_driver_unregister(&rtc_dm355evm_driver);
172}
173module_exit(dm355evm_rtc_exit);
174
175MODULE_LICENSE("GPL");