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
au1xtoy_rtc_read_time(struct device * dev,struct rtc_time * tm)31 static int au1xtoy_rtc_read_time(struct device *dev, struct rtc_time *tm)
32 {
33 unsigned long t;
34
35 t = alchemy_rdsys(AU1000_SYS_TOYREAD);
36
37 rtc_time_to_tm(t, tm);
38
39 return 0;
40 }
41
au1xtoy_rtc_set_time(struct device * dev,struct rtc_time * tm)42 static 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 alchemy_wrsys(t, AU1000_SYS_TOYWRITE);
49
50 /* wait for the pending register write to succeed. This can
51 * take up to 6 seconds...
52 */
53 while (alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_C0S)
54 msleep(1);
55
56 return 0;
57 }
58
59 static const struct rtc_class_ops au1xtoy_rtc_ops = {
60 .read_time = au1xtoy_rtc_read_time,
61 .set_time = au1xtoy_rtc_set_time,
62 };
63
au1xtoy_rtc_probe(struct platform_device * pdev)64 static int au1xtoy_rtc_probe(struct platform_device *pdev)
65 {
66 struct rtc_device *rtcdev;
67 unsigned long t;
68 int ret;
69
70 t = alchemy_rdsys(AU1000_SYS_CNTRCTRL);
71 if (!(t & CNTR_OK)) {
72 dev_err(&pdev->dev, "counters not working; aborting.\n");
73 ret = -ENODEV;
74 goto out_err;
75 }
76
77 ret = -ETIMEDOUT;
78
79 /* set counter0 tickrate to 1Hz if necessary */
80 if (alchemy_rdsys(AU1000_SYS_TOYTRIM) != 32767) {
81 /* wait until hardware gives access to TRIM register */
82 t = 0x00100000;
83 while ((alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_T0S) && --t)
84 msleep(1);
85
86 if (!t) {
87 /* timed out waiting for register access; assume
88 * counters are unusable.
89 */
90 dev_err(&pdev->dev, "timeout waiting for access\n");
91 goto out_err;
92 }
93
94 /* set 1Hz TOY tick rate */
95 alchemy_wrsys(32767, AU1000_SYS_TOYTRIM);
96 }
97
98 /* wait until the hardware allows writes to the counter reg */
99 while (alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_C0S)
100 msleep(1);
101
102 rtcdev = devm_rtc_device_register(&pdev->dev, "rtc-au1xxx",
103 &au1xtoy_rtc_ops, THIS_MODULE);
104 if (IS_ERR(rtcdev)) {
105 ret = PTR_ERR(rtcdev);
106 goto out_err;
107 }
108
109 platform_set_drvdata(pdev, rtcdev);
110
111 return 0;
112
113 out_err:
114 return ret;
115 }
116
117 static struct platform_driver au1xrtc_driver = {
118 .driver = {
119 .name = "rtc-au1xxx",
120 },
121 };
122
123 module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
124
125 MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
126 MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
127 MODULE_LICENSE("GPL");
128 MODULE_ALIAS("platform:rtc-au1xxx");
129