LXR 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
  31static 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
  42static 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
  59static const struct rtc_class_ops au1xtoy_rtc_ops = {
  60        .read_time      = au1xtoy_rtc_read_time,
  61        .set_time       = au1xtoy_rtc_set_time,
  62};
  63
  64static 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
 110static struct platform_driver au1xrtc_driver = {
 111        .driver         = {
 112                .name   = "rtc-au1xxx",
 113        },
 114};
 115
 116module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
 117
 118MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
 119MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
 120MODULE_LICENSE("GPL");
 121MODULE_ALIAS("platform:rtc-au1xxx");
 122