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_time64_to_tm(t, tm);
  38
  39         return 0;
  40 }
  41
  42 static int au1xtoy_rtc_set_time(struct device *dev, struct rtc_time *tm)
  43 {
  44         unsigned long t;
  45
  46         t = rtc_tm_to_time64(tm);
  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
  69         t = alchemy_rdsys(AU1000_SYS_CNTRCTRL);
  70         if (!(t & CNTR_OK)) {
  71                 dev_err(&pdev->dev, "counters not working; aborting.\n");
  72                 return -ENODEV;
  73         }
  74
  75         /* set counter0 tickrate to 1Hz if necessary */
  76         if (alchemy_rdsys(AU1000_SYS_TOYTRIM) != 32767) {
  77                 /* wait until hardware gives access to TRIM register */
  78                 t = 0x00100000;
  79                 while ((alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_T0S) && --t)
  80                         msleep(1);
  81
  82                 if (!t) {
  83                         /* timed out waiting for register access; assume
  84                          * counters are unusable.
  85                          */
  86                         dev_err(&pdev->dev, "timeout waiting for access\n");
  87                         return -ETIMEDOUT;
  88                 }
  89
  90                 /* set 1Hz TOY tick rate */
  91                 alchemy_wrsys(32767, AU1000_SYS_TOYTRIM);
  92         }
  93
  94         /* wait until the hardware allows writes to the counter reg */
  95         while (alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_C0S)
  96                 msleep(1);
  97
  98         rtcdev = devm_rtc_allocate_device(&pdev->dev);
  99         if (IS_ERR(rtcdev))
 100                 return PTR_ERR(rtcdev);
 101
 102         rtcdev->ops = &au1xtoy_rtc_ops;
 103         rtcdev->range_max = U32_MAX;
 104
 105         platform_set_drvdata(pdev, rtcdev);
 106
 107         return devm_rtc_register_device(rtcdev);
 108 }
 109
 110 static struct platform_driver au1xrtc_driver = {
 111         .driver         = {
 112                 .name   = "rtc-au1xxx",
 113         },
 114 };
 115
 116 module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
 117
 118 MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
 119 MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
 120 MODULE_LICENSE("GPL");
 121 MODULE_ALIAS("platform:rtc-au1xxx");