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 } 59