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Linux/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 
 31 static 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 
 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         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 
 60 static struct rtc_class_ops au1xtoy_rtc_ops = {
 61         .read_time      = au1xtoy_rtc_read_time,
 62         .set_time       = au1xtoy_rtc_set_time,
 63 };
 64 
 65 static int 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 = devm_rtc_device_register(&pdev->dev, "rtc-au1xxx",
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 
115 out_err:
116         return ret;
117 }
118 
119 static struct platform_driver au1xrtc_driver = {
120         .driver         = {
121                 .name   = "rtc-au1xxx",
122                 .owner  = THIS_MODULE,
123         },
124 };
125 
126 module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
127 
128 MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
129 MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
130 MODULE_LICENSE("GPL");
131 MODULE_ALIAS("platform:rtc-au1xxx");
132 

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