linux/drivers/rtc/rtc-au1xxx.c
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   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 = au_readl(SYS_TOYREAD);
  36
  37        rtc_time_to_tm(t, tm);
  38
  39        return rtc_valid_tm(tm);
  40}
  41
  42static 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
  60static struct rtc_class_ops au1xtoy_rtc_ops = {
  61        .read_time      = au1xtoy_rtc_read_time,
  62        .set_time       = au1xtoy_rtc_set_time,
  63};
  64
  65static 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
 115out_err:
 116        return ret;
 117}
 118
 119static struct platform_driver au1xrtc_driver = {
 120        .driver         = {
 121                .name   = "rtc-au1xxx",
 122                .owner  = THIS_MODULE,
 123        },
 124};
 125
 126module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
 127
 128MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
 129MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
 130MODULE_LICENSE("GPL");
 131MODULE_ALIAS("platform:rtc-au1xxx");
 132
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