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 = alchemy_rdsys(AU1000_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         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
  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");