drivers/rtc/rtc-sun4v.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* rtc-sun4v.c: Hypervisor based RTC for SUN4V systems.
   3  *
   4  * Author: David S. Miller
   5  *
   6  * Copyright (C) 2008 David S. Miller <davem@davemloft.net>
   7  */
   8
   9 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  10
  11 #include <linux/kernel.h>
  12 #include <linux/delay.h>
  13 #include <linux/init.h>
  14 #include <linux/rtc.h>
  15 #include <linux/platform_device.h>
  16
  17 #include <asm/hypervisor.h>
  18
  19 static unsigned long hypervisor_get_time(void)
  20 {
  21         unsigned long ret, time;
  22         int retries = 10000;
  23
  24 retry:
  25         ret = sun4v_tod_get(&time);
  26         if (ret == HV_EOK)
  27                 return time;
  28         if (ret == HV_EWOULDBLOCK) {
  29                 if (--retries > 0) {
  30                         udelay(100);
  31                         goto retry;
  32                 }
  33                 pr_warn("tod_get() timed out.\n");
  34                 return 0;
  35         }
  36         pr_warn("tod_get() not supported.\n");
  37         return 0;
  38 }
  39
  40 static int sun4v_read_time(struct device *dev, struct rtc_time *tm)
  41 {
  42         rtc_time64_to_tm(hypervisor_get_time(), tm);
  43         return 0;
  44 }
  45
  46 static int hypervisor_set_time(unsigned long secs)
  47 {
  48         unsigned long ret;
  49         int retries = 10000;
  50
  51 retry:
  52         ret = sun4v_tod_set(secs);
  53         if (ret == HV_EOK)
  54                 return 0;
  55         if (ret == HV_EWOULDBLOCK) {
  56                 if (--retries > 0) {
  57                         udelay(100);
  58                         goto retry;
  59                 }
  60                 pr_warn("tod_set() timed out.\n");
  61                 return -EAGAIN;
  62         }
  63         pr_warn("tod_set() not supported.\n");
  64         return -EOPNOTSUPP;
  65 }
  66
  67 static int sun4v_set_time(struct device *dev, struct rtc_time *tm)
  68 {
  69         return hypervisor_set_time(rtc_tm_to_time64(tm));
  70 }
  71
  72 static const struct rtc_class_ops sun4v_rtc_ops = {
  73         .read_time      = sun4v_read_time,
  74         .set_time       = sun4v_set_time,
  75 };
  76
  77 static int __init sun4v_rtc_probe(struct platform_device *pdev)
  78 {
  79         struct rtc_device *rtc;
  80
  81         rtc = devm_rtc_allocate_device(&pdev->dev);
  82         if (IS_ERR(rtc))
  83                 return PTR_ERR(rtc);
  84
  85         rtc->ops = &sun4v_rtc_ops;
  86         rtc->range_max = U64_MAX;
  87         platform_set_drvdata(pdev, rtc);
  88
  89         return devm_rtc_register_device(rtc);
  90 }
  91
  92 static struct platform_driver sun4v_rtc_driver = {
  93         .driver         = {
  94                 .name   = "rtc-sun4v",
  95         },
  96 };
  97
  98 builtin_platform_driver_probe(sun4v_rtc_driver, sun4v_rtc_probe);