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
28void __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}
59