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
27void __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