nes-proj/cpu/x86/drivers/legacy_pc/rtc.c

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/*
* Copyright (C) 2015, Intel Corporation. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the copyright holder nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "drivers/legacy_pc/rtc.h"
#include "drivers/legacy_pc/pic.h"
#include "drivers/legacy_pc/nmi.h"
#include "helpers.h"
#include "interrupt.h"
#define RTC_INDEX_REGISTER 0x70
#define RTC_TARGET_REGISTER 0x71
#define RTC_IRQ 8
#define RTC_INT PIC_INT(RTC_IRQ)
static void (*user_callback)(void);
static void
rtc_handler()
{
user_callback();
/* Clear Register C otherwise interrupts will not happen again.
* Register C is automatically cleared when it is read so we do
* a dummy read to clear it.
*/
outb(RTC_INDEX_REGISTER, 0x0C);
inb(RTC_TARGET_REGISTER);
/* Issue the End of Interrupt to PIC */
pic_eoi(RTC_IRQ);
}
/*---------------------------------------------------------------------------*/
/* Initialize the Real Time Clock.
* @frequency: RTC has very specific values for frequency. They are: 2, 4, 8,
* 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, and 8192 Hz.
* value otherwise it will not work properly.
* @callback: This callback is called every time the RTC IRQ is raised.
* It is executed in interrupt context.
*/
void
rtc_init(rtc_frequency_t frequency, void (*callback)(void))
{
uint8_t reg_a, reg_b;
user_callback = callback;
SET_INTERRUPT_HANDLER(RTC_INT, 0, rtc_handler);
nmi_disable();
/* Select interrupt period to 7.8125 ms */
outb(RTC_INDEX_REGISTER, 0x8A);
reg_a = inb(RTC_TARGET_REGISTER);
reg_a &= 0xF0;
reg_a |= frequency;
outb(RTC_INDEX_REGISTER, 0x8A);
outb(RTC_TARGET_REGISTER, reg_a);
/* Enable periodic interrupt */
outb(RTC_INDEX_REGISTER, 0x8B);
reg_b = inb(RTC_TARGET_REGISTER);
outb(RTC_INDEX_REGISTER, 0x8B);
outb(RTC_TARGET_REGISTER, reg_b | BIT(6));
nmi_enable();
pic_unmask_irq(RTC_IRQ);
}