arch/arm/mach-footbridge/isa-rtc.c

   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 }