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 int au1xtoy_rtc_remove(struct platform_device *pdev)
 120 {
 121         platform_set_drvdata(pdev, NULL);
 122
 123         return 0;
 124 }
 125
 126 static struct platform_driver au1xrtc_driver = {
 127         .driver         = {
 128                 .name   = "rtc-au1xxx",
 129                 .owner  = THIS_MODULE,
 130         },
 131         .remove         = au1xtoy_rtc_remove,
 132 };
 133
 134 module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
 135
 136 MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
 137 MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
 138 MODULE_LICENSE("GPL");
 139 MODULE_ALIAS("platform:rtc-au1xxx");