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