drivers/rtc/rtc-au1xxx.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Au1xxx counter0 (aka Time-Of-Year counter) RTC interface driver.
   4  *
   5  * Copyright (C) 2008 Manuel Lauss <mano@roarinelk.homelinux.net>
   6  */
   7
   8 /* All current Au1xxx SoCs have 2 counters fed by an external 32.768 kHz
   9  * crystal. Counter 0, which keeps counting during sleep/powerdown, is
  10  * used to count seconds since the beginning of the unix epoch.
  11  *
  12  * The counters must be configured and enabled by bootloader/board code;
  13  * no checks as to whether they really get a proper 32.768kHz clock are
  14  * made as this would take far too long.
  15  */
  16
  17 #include <linux/module.h>
  18 #include <linux/kernel.h>
  19 #include <linux/rtc.h>
  20 #include <linux/init.h>
  21 #include <linux/platform_device.h>
  22 #include <linux/io.h>
  23 #include <asm/mach-au1x00/au1000.h>
  24
  25 /* 32kHz clock enabled and detected */
  26 #define CNTR_OK (SYS_CNTRL_E0 | SYS_CNTRL_32S)
  27
  28 static int au1xtoy_rtc_read_time(struct device *dev, struct rtc_time *tm)
  29 {
  30         unsigned long t;
  31
  32         t = alchemy_rdsys(AU1000_SYS_TOYREAD);
  33
  34         rtc_time64_to_tm(t, tm);
  35
  36         return 0;
  37 }
  38
  39 static int au1xtoy_rtc_set_time(struct device *dev, struct rtc_time *tm)
  40 {
  41         unsigned long t;
  42
  43         t = rtc_tm_to_time64(tm);
  44
  45         alchemy_wrsys(t, AU1000_SYS_TOYWRITE);
  46
  47         /* wait for the pending register write to succeed.  This can
  48          * take up to 6 seconds...
  49          */
  50         while (alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_C0S)
  51                 msleep(1);
  52
  53         return 0;
  54 }
  55
  56 static const struct rtc_class_ops au1xtoy_rtc_ops = {
  57         .read_time      = au1xtoy_rtc_read_time,
  58         .set_time       = au1xtoy_rtc_set_time,
  59 };
  60
  61 static int au1xtoy_rtc_probe(struct platform_device *pdev)
  62 {
  63         struct rtc_device *rtcdev;
  64         unsigned long t;
  65
  66         t = alchemy_rdsys(AU1000_SYS_CNTRCTRL);
  67         if (!(t & CNTR_OK)) {
  68                 dev_err(&pdev->dev, "counters not working; aborting.\n");
  69                 return -ENODEV;
  70         }
  71
  72         /* set counter0 tickrate to 1Hz if necessary */
  73         if (alchemy_rdsys(AU1000_SYS_TOYTRIM) != 32767) {
  74                 /* wait until hardware gives access to TRIM register */
  75                 t = 0x00100000;
  76                 while ((alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_T0S) && --t)
  77                         msleep(1);
  78
  79                 if (!t) {
  80                         /* timed out waiting for register access; assume
  81                          * counters are unusable.
  82                          */
  83                         dev_err(&pdev->dev, "timeout waiting for access\n");
  84                         return -ETIMEDOUT;
  85                 }
  86
  87                 /* set 1Hz TOY tick rate */
  88                 alchemy_wrsys(32767, AU1000_SYS_TOYTRIM);
  89         }
  90
  91         /* wait until the hardware allows writes to the counter reg */
  92         while (alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_C0S)
  93                 msleep(1);
  94
  95         rtcdev = devm_rtc_allocate_device(&pdev->dev);
  96         if (IS_ERR(rtcdev))
  97                 return PTR_ERR(rtcdev);
  98
  99         rtcdev->ops = &au1xtoy_rtc_ops;
 100         rtcdev->range_max = U32_MAX;
 101
 102         platform_set_drvdata(pdev, rtcdev);
 103
 104         return devm_rtc_register_device(rtcdev);
 105 }
 106
 107 static struct platform_driver au1xrtc_driver = {
 108         .driver         = {
 109                 .name   = "rtc-au1xxx",
 110         },
 111 };
 112
 113 module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
 114
 115 MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
 116 MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
 117 MODULE_LICENSE("GPL");
 118 MODULE_ALIAS("platform:rtc-au1xxx");