1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * arch/arm/mach-footbridge/isa-rtc.c
4 *
5 * Copyright (C) 1998 Russell King.
6 * Copyright (C) 1998 Phil Blundell
7 *
8 * CATS has a real-time clock, though the evaluation board doesn't.
9 *
10 * Changelog:
11 * 21-Mar-1998 RMK Created
12 * 27-Aug-1998 PJB CATS support
13 * 28-Dec-1998 APH Made leds optional
14 * 20-Jan-1999 RMK Started merge of EBSA285, CATS and NetWinder
15 * 16-Mar-1999 RMK More support for EBSA285-like machines with RTCs in
16 */
17
18 #define RTC_PORT(x) (0x70+(x))
19 #define RTC_ALWAYS_BCD 0
20
21 #include <linux/init.h>
22 #include <linux/mc146818rtc.h>
23 #include <linux/io.h>
24
25 #include "common.h"
26
27 void __init isa_rtc_init(void)
28 {
29 int reg_d, reg_b;
30
31 /*
32 * Probe for the RTC.
33 */
34 reg_d = CMOS_READ(RTC_REG_D);
35
36 /*
37 * make sure the divider is set
38 */
39 CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_REG_A);
40
41 /*
42 * Set control reg B
43 * (24 hour mode, update enabled)
44 */
45 reg_b = CMOS_READ(RTC_REG_B) & 0x7f;
46 reg_b |= 2;
47 CMOS_WRITE(reg_b, RTC_REG_B);
48
49 if ((CMOS_READ(RTC_REG_A) & 0x7f) == RTC_REF_CLCK_32KHZ &&
50 CMOS_READ(RTC_REG_B) == reg_b) {
51 /*
52 * We have a RTC. Check the battery
53 */
54 if ((reg_d & 0x80) == 0)
55 printk(KERN_WARNING "RTC: *** warning: CMOS battery bad\n");
56 }
57 }
58
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