Root/drivers/rtc/rtc-au1xxx.c

1/*
2 * Au1xxx counter0 (aka Time-Of-Year counter) RTC interface driver.
3 *
4 * Copyright (C) 2008 Manuel Lauss <mano@roarinelk.homelinux.net>
5 *
6 * This file is subject to the terms and conditions of the GNU General Public
7 * License. See the file "COPYING" in the main directory of this archive
8 * for more details.
9 */
10
11/* All current Au1xxx SoCs have 2 counters fed by an external 32.768 kHz
12 * crystal. Counter 0, which keeps counting during sleep/powerdown, is
13 * used to count seconds since the beginning of the unix epoch.
14 *
15 * The counters must be configured and enabled by bootloader/board code;
16 * no checks as to whether they really get a proper 32.768kHz clock are
17 * made as this would take far too long.
18 */
19
20#include <linux/module.h>
21#include <linux/kernel.h>
22#include <linux/rtc.h>
23#include <linux/init.h>
24#include <linux/platform_device.h>
25#include <linux/io.h>
26#include <asm/mach-au1x00/au1000.h>
27
28/* 32kHz clock enabled and detected */
29#define CNTR_OK (SYS_CNTRL_E0 | SYS_CNTRL_32S)
30
31static int au1xtoy_rtc_read_time(struct device *dev, struct rtc_time *tm)
32{
33    unsigned long t;
34
35    t = au_readl(SYS_TOYREAD);
36
37    rtc_time_to_tm(t, tm);
38
39    return rtc_valid_tm(tm);
40}
41
42static int au1xtoy_rtc_set_time(struct device *dev, struct rtc_time *tm)
43{
44    unsigned long t;
45
46    rtc_tm_to_time(tm, &t);
47
48    au_writel(t, SYS_TOYWRITE);
49    au_sync();
50
51    /* wait for the pending register write to succeed. This can
52     * take up to 6 seconds...
53     */
54    while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C0S)
55        msleep(1);
56
57    return 0;
58}
59
60static struct rtc_class_ops au1xtoy_rtc_ops = {
61    .read_time = au1xtoy_rtc_read_time,
62    .set_time = au1xtoy_rtc_set_time,
63};
64
65static int __devinit au1xtoy_rtc_probe(struct platform_device *pdev)
66{
67    struct rtc_device *rtcdev;
68    unsigned long t;
69    int ret;
70
71    t = au_readl(SYS_COUNTER_CNTRL);
72    if (!(t & CNTR_OK)) {
73        dev_err(&pdev->dev, "counters not working; aborting.\n");
74        ret = -ENODEV;
75        goto out_err;
76    }
77
78    ret = -ETIMEDOUT;
79
80    /* set counter0 tickrate to 1Hz if necessary */
81    if (au_readl(SYS_TOYTRIM) != 32767) {
82        /* wait until hardware gives access to TRIM register */
83        t = 0x00100000;
84        while ((au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_T0S) && --t)
85            msleep(1);
86
87        if (!t) {
88            /* timed out waiting for register access; assume
89             * counters are unusable.
90             */
91            dev_err(&pdev->dev, "timeout waiting for access\n");
92            goto out_err;
93        }
94
95        /* set 1Hz TOY tick rate */
96        au_writel(32767, SYS_TOYTRIM);
97        au_sync();
98    }
99
100    /* wait until the hardware allows writes to the counter reg */
101    while (au_readl(SYS_COUNTER_CNTRL) & SYS_CNTRL_C0S)
102        msleep(1);
103
104    rtcdev = rtc_device_register("rtc-au1xxx", &pdev->dev,
105                     &au1xtoy_rtc_ops, THIS_MODULE);
106    if (IS_ERR(rtcdev)) {
107        ret = PTR_ERR(rtcdev);
108        goto out_err;
109    }
110
111    platform_set_drvdata(pdev, rtcdev);
112
113    return 0;
114
115out_err:
116    return ret;
117}
118
119static int __devexit au1xtoy_rtc_remove(struct platform_device *pdev)
120{
121    struct rtc_device *rtcdev = platform_get_drvdata(pdev);
122
123    rtc_device_unregister(rtcdev);
124    platform_set_drvdata(pdev, NULL);
125
126    return 0;
127}
128
129static struct platform_driver au1xrtc_driver = {
130    .driver = {
131        .name = "rtc-au1xxx",
132        .owner = THIS_MODULE,
133    },
134    .remove = __devexit_p(au1xtoy_rtc_remove),
135};
136
137static int __init au1xtoy_rtc_init(void)
138{
139    return platform_driver_probe(&au1xrtc_driver, au1xtoy_rtc_probe);
140}
141
142static void __exit au1xtoy_rtc_exit(void)
143{
144    platform_driver_unregister(&au1xrtc_driver);
145}
146
147module_init(au1xtoy_rtc_init);
148module_exit(au1xtoy_rtc_exit);
149
150MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
151MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
152MODULE_LICENSE("GPL");
153MODULE_ALIAS("platform:rtc-au1xxx");
154

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