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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/arch/arm/mach-footbridge/isa-rtc.c
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// SPDX-License-Identifier: GPL-2.0

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/*

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

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 *

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 *  Copyright (C) 1998 Russell King.

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 *  Copyright (C) 1998 Phil Blundell

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 *

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 * CATS has a real-time clock, though the evaluation board doesn't.

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 *

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 * Changelog:

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 *  21-Mar-1998	RMK	Created

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 *  27-Aug-1998	PJB	CATS support

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 *  28-Dec-1998	APH	Made leds optional

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 *  20-Jan-1999	RMK	Started merge of EBSA285, CATS and NetWinder

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 *  16-Mar-1999	RMK	More support for EBSA285-like machines with RTCs in

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 */

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#define RTC_PORT(x)		(0x70+(x))

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#define RTC_ALWAYS_BCD		0

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#include <linux/init.h>

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#include <linux/mc146818rtc.h>

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#include <linux/io.h>

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#include "common.h"

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void __init isa_rtc_init(void)

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{

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	int reg_d, reg_b;

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	/*

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	 * Probe for the RTC.

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	 */

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	reg_d = CMOS_READ(RTC_REG_D);

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	/*

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	 * make sure the divider is set

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	 */

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	CMOS_WRITE(RTC_REF_CLCK_32KHZ, RTC_REG_A);

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	/*

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	 * Set control reg B

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	 *   (24 hour mode, update enabled)

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	 */

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	reg_b = CMOS_READ(RTC_REG_B) & 0x7f;

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	reg_b |= 2;

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	CMOS_WRITE(reg_b, RTC_REG_B);

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	if ((CMOS_READ(RTC_REG_A) & 0x7f) == RTC_REF_CLCK_32KHZ &&

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	    CMOS_READ(RTC_REG_B) == reg_b) {

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		/*

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		 * We have a RTC.  Check the battery

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		 */

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		if ((reg_d & 0x80) == 0)

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			printk(KERN_WARNING "RTC: *** warning: CMOS battery bad\n");

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	}

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}

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