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/bcd.h>
24 #include <linux/io.h>
25
26 #include "common.h"
27
28 void __init isa_rtc_init(void)
29 {
30 int reg_d, reg_b;
31
32 /*
33 * Probe for the RTC.
34 */
35 reg_d = CMOS_READ(RTC_REG_D);
36
37 /*
38 * make sure the divider is set
39 */
40 CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_REG_A);
41
42 /*
43 * Set control reg B
44 * (24 hour mode, update enabled)
45 */
46 reg_b = CMOS_READ(RTC_REG_B) & 0x7f;
47 reg_b |= 2;
48 CMOS_WRITE(reg_b, RTC_REG_B);
49
50 if ((CMOS_READ(RTC_REG_A) & 0x7f) == RTC_REF_CLCK_32KHZ &&
51 CMOS_READ(RTC_REG_B) == reg_b) {
52 /*
53 * We have a RTC. Check the battery
54 */
55 if ((reg_d & 0x80) == 0)
56 printk(KERN_WARNING "RTC: *** warning: CMOS battery bad\n");
57 }
58 }