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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 
 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_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         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 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         int ret;
 69 
 70         t = alchemy_rdsys(AU1000_SYS_CNTRCTRL);
 71         if (!(t & CNTR_OK)) {
 72                 dev_err(&pdev->dev, "counters not working; aborting.\n");
 73                 ret = -ENODEV;
 74                 goto out_err;
 75         }
 76 
 77         ret = -ETIMEDOUT;
 78 
 79         /* set counter0 tickrate to 1Hz if necessary */
 80         if (alchemy_rdsys(AU1000_SYS_TOYTRIM) != 32767) {
 81                 /* wait until hardware gives access to TRIM register */
 82                 t = 0x00100000;
 83                 while ((alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_T0S) && --t)
 84                         msleep(1);
 85 
 86                 if (!t) {
 87                         /* timed out waiting for register access; assume
 88                          * counters are unusable.
 89                          */
 90                         dev_err(&pdev->dev, "timeout waiting for access\n");
 91                         goto out_err;
 92                 }
 93 
 94                 /* set 1Hz TOY tick rate */
 95                 alchemy_wrsys(32767, AU1000_SYS_TOYTRIM);
 96         }
 97 
 98         /* wait until the hardware allows writes to the counter reg */
 99         while (alchemy_rdsys(AU1000_SYS_CNTRCTRL) & SYS_CNTRL_C0S)
100                 msleep(1);
101 
102         rtcdev = devm_rtc_device_register(&pdev->dev, "rtc-au1xxx",
103                                      &au1xtoy_rtc_ops, THIS_MODULE);
104         if (IS_ERR(rtcdev)) {
105                 ret = PTR_ERR(rtcdev);
106                 goto out_err;
107         }
108 
109         platform_set_drvdata(pdev, rtcdev);
110 
111         return 0;
112 
113 out_err:
114         return ret;
115 }
116 
117 static struct platform_driver au1xrtc_driver = {
118         .driver         = {
119                 .name   = "rtc-au1xxx",
120                 .owner  = THIS_MODULE,
121         },
122 };
123 
124 module_platform_driver_probe(au1xrtc_driver, au1xtoy_rtc_probe);
125 
126 MODULE_DESCRIPTION("Au1xxx TOY-counter-based RTC driver");
127 MODULE_AUTHOR("Manuel Lauss <manuel.lauss@gmail.com>");
128 MODULE_LICENSE("GPL");
129 MODULE_ALIAS("platform:rtc-au1xxx");
130 

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