rtc-efi.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * rtc-efi: RTC Class Driver for EFI-based systems
  4 *
  5 * Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
  6 *
  7 * Author: dann frazier <dannf@dannf.org>
  8 * Based on efirtc.c by Stephane Eranian
  9 */
 10
 11#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 12
 13#include <linux/kernel.h>
 14#include <linux/module.h>
 15#include <linux/stringify.h>
 16#include <linux/time.h>
 17#include <linux/platform_device.h>
 18#include <linux/rtc.h>
 19#include <linux/efi.h>
 20
 21#define EFI_ISDST (EFI_TIME_ADJUST_DAYLIGHT|EFI_TIME_IN_DAYLIGHT)
 22
 23/*
 24 * returns day of the year [0-365]
 25 */
 26static inline int
 27compute_yday(efi_time_t *eft)
 28{
 29	/* efi_time_t.month is in the [1-12] so, we need -1 */
 30	return rtc_year_days(eft->day, eft->month - 1, eft->year);
 31}
 32
 33/*
 34 * returns day of the week [0-6] 0=Sunday
 35 */
 36static int
 37compute_wday(efi_time_t *eft, int yday)
 38{
 39	int ndays = eft->year * (365 % 7)
 40		    + (eft->year - 1) / 4
 41		    - (eft->year - 1) / 100
 42		    + (eft->year - 1) / 400
 43		    + yday;
 44
 45	/*
 46	 * 1/1/0000 may or may not have been a Sunday (if it ever existed at
 47	 * all) but assuming it was makes this calculation work correctly.
 48	 */
 49	return ndays % 7;
 50}
 51
 52static void
 53convert_to_efi_time(struct rtc_time *wtime, efi_time_t *eft)
 54{
 55	eft->year	= wtime->tm_year + 1900;
 56	eft->month	= wtime->tm_mon + 1;
 57	eft->day	= wtime->tm_mday;
 58	eft->hour	= wtime->tm_hour;
 59	eft->minute	= wtime->tm_min;
 60	eft->second	= wtime->tm_sec;
 61	eft->nanosecond = 0;
 62	eft->daylight	= wtime->tm_isdst ? EFI_ISDST : 0;
 63	eft->timezone	= EFI_UNSPECIFIED_TIMEZONE;
 64}
 65
 66static bool
 67convert_from_efi_time(efi_time_t *eft, struct rtc_time *wtime)
 68{
 69	memset(wtime, 0, sizeof(*wtime));
 70
 71	if (eft->second >= 60)
 72		return false;
 73	wtime->tm_sec  = eft->second;
 74
 75	if (eft->minute >= 60)
 76		return false;
 77	wtime->tm_min  = eft->minute;
 78
 79	if (eft->hour >= 24)
 80		return false;
 81	wtime->tm_hour = eft->hour;
 82
 83	if (!eft->day || eft->day > 31)
 84		return false;
 85	wtime->tm_mday = eft->day;
 86
 87	if (!eft->month || eft->month > 12)
 88		return false;
 89	wtime->tm_mon  = eft->month - 1;
 90
 91	if (eft->year < 1900 || eft->year > 9999)
 92		return false;
 93	wtime->tm_year = eft->year - 1900;
 94
 95	/* day in the year [1-365]*/
 96	wtime->tm_yday = compute_yday(eft);
 97
 98	/* day of the week [0-6], Sunday=0 */
 99	wtime->tm_wday = compute_wday(eft, wtime->tm_yday);
100
101	switch (eft->daylight & EFI_ISDST) {
102	case EFI_ISDST:
103		wtime->tm_isdst = 1;
104		break;
105	case EFI_TIME_ADJUST_DAYLIGHT:
106		wtime->tm_isdst = 0;
107		break;
108	default:
109		wtime->tm_isdst = -1;
110	}
111
112	return true;
113}
114
115static int efi_read_time(struct device *dev, struct rtc_time *tm)
116{
117	efi_status_t status;
118	efi_time_t eft;
119	efi_time_cap_t cap;
120
121	status = efi.get_time(&eft, &cap);
122
123	if (status != EFI_SUCCESS) {
124		/* should never happen */
125		dev_err_once(dev, "can't read time\n");
126		return -EINVAL;
127	}
128
129	if (!convert_from_efi_time(&eft, tm))
130		return -EIO;
131
132	return 0;
133}
134
135static int efi_set_time(struct device *dev, struct rtc_time *tm)
136{
137	efi_status_t status;
138	efi_time_t eft;
139
140	convert_to_efi_time(tm, &eft);
141
142	status = efi.set_time(&eft);
143
144	return status == EFI_SUCCESS ? 0 : -EINVAL;
145}
146
147static int efi_procfs(struct device *dev, struct seq_file *seq)
148{
149	efi_time_t        eft;
150	efi_time_cap_t    cap;
151
152	memset(&eft, 0, sizeof(eft));
153	memset(&cap, 0, sizeof(cap));
154
155	efi.get_time(&eft, &cap);
156
157	seq_printf(seq,
158		   "Time\t\t: %u:%u:%u.%09u\n"
159		   "Date\t\t: %u-%u-%u\n"
160		   "Daylight\t: %u\n",
161		   eft.hour, eft.minute, eft.second, eft.nanosecond,
162		   eft.year, eft.month, eft.day,
163		   eft.daylight);
164
165	if (eft.timezone == EFI_UNSPECIFIED_TIMEZONE)
166		seq_puts(seq, "Timezone\t: unspecified\n");
167	else
168		/* XXX fixme: convert to string? */
169		seq_printf(seq, "Timezone\t: %u\n", eft.timezone);
170
171	/*
172	 * now prints the capabilities
173	 */
174	seq_printf(seq,
175		   "Resolution\t: %u\n"
176		   "Accuracy\t: %u\n"
177		   "SetstoZero\t: %u\n",
178		   cap.resolution, cap.accuracy, cap.sets_to_zero);
179
180	return 0;
181}
182
183static const struct rtc_class_ops efi_rtc_ops = {
184	.read_time	= efi_read_time,
185	.set_time	= efi_set_time,
186	.proc		= efi_procfs,
187};
188
189static int __init efi_rtc_probe(struct platform_device *dev)
190{
191	struct rtc_device *rtc;
192	efi_time_t eft;
193	efi_time_cap_t cap;
194
195	/* First check if the RTC is usable */
196	if (efi.get_time(&eft, &cap) != EFI_SUCCESS)
197		return -ENODEV;
198
199	rtc = devm_rtc_allocate_device(&dev->dev);
200	if (IS_ERR(rtc))
201		return PTR_ERR(rtc);
202
203	platform_set_drvdata(dev, rtc);
204
205	rtc->ops = &efi_rtc_ops;
206	clear_bit(RTC_FEATURE_ALARM, rtc->features);
207
208	device_init_wakeup(&dev->dev, true);
209
210	return devm_rtc_register_device(rtc);
211}
212
213static struct platform_driver efi_rtc_driver = {
214	.driver = {
215		.name = "rtc-efi",
216	},
217};
218
219module_platform_driver_probe(efi_rtc_driver, efi_rtc_probe);
220
221MODULE_AUTHOR("dann frazier <dannf@dannf.org>");
222MODULE_LICENSE("GPL");
223MODULE_DESCRIPTION("EFI RTC driver");
224MODULE_ALIAS("platform:rtc-efi");