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