diff options
author | David Brownell <dbrownell@users.sourceforge.net> | 2009-02-04 18:12:01 -0500 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-02-05 15:56:46 -0500 |
commit | afd8d0f940ba5078f38e435440089117ac7d9eb4 (patch) | |
tree | 1f494035691b04175ed21ed3703593ce37957925 /drivers | |
parent | 77a592655cdb8d838b85fd7ecf8f36fd2870abfc (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>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/rtc/Kconfig | 6 | ||||
-rw-r--r-- | drivers/rtc/Makefile | 1 | ||||
-rw-r--r-- | drivers/rtc/rtc-dm355evm.c | 175 |
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 | ||
244 | config 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 | |||
244 | config RTC_DRV_TWL92330 | 250 | config 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-$(CONFIG_RTC_DRV_AT91SAM9) += rtc-at91sam9.o | |||
23 | obj-$(CONFIG_RTC_DRV_AU1XXX) += rtc-au1xxx.o | 23 | obj-$(CONFIG_RTC_DRV_AU1XXX) += rtc-au1xxx.o |
24 | obj-$(CONFIG_RTC_DRV_BFIN) += rtc-bfin.o | 24 | obj-$(CONFIG_RTC_DRV_BFIN) += rtc-bfin.o |
25 | obj-$(CONFIG_RTC_DRV_CMOS) += rtc-cmos.o | 25 | obj-$(CONFIG_RTC_DRV_CMOS) += rtc-cmos.o |
26 | obj-$(CONFIG_RTC_DRV_DM355EVM) += rtc-dm355evm.o | ||
26 | obj-$(CONFIG_RTC_DRV_DS1216) += rtc-ds1216.o | 27 | obj-$(CONFIG_RTC_DRV_DS1216) += rtc-ds1216.o |
27 | obj-$(CONFIG_RTC_DRV_DS1286) += rtc-ds1286.o | 28 | obj-$(CONFIG_RTC_DRV_DS1286) += rtc-ds1286.o |
28 | obj-$(CONFIG_RTC_DRV_DS1302) += rtc-ds1302.o | 29 | obj-$(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 | */ | ||
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"); | ||