cb0510ebcf
According to [1], we should disable non-maskable and maskable interrupts while initializing RTC. Otherwise, the RTC may be left in an undefined state (non-functional) if an interrupt occurs. Currently, maskable interrupts are already disabled, but NMI is not. This patch adds helpers APIs to enable/disable non-maskable interrupts (NMI) and changes rtc_init() to disable NMI while initializing the RTC. NMI enable/disable code is legacy-PC specific therefore it was put in driver/legacy_pc/ directory. Regarding the RTC initialization changes, just calling nmi_disable() and nmi_enable is not enough since NMI and RTC share the same IO port. So We should also set the NMI_ENABLE bit while selecting the RTC_INDEX. Additionally, the nmi_disable() call is not strictly required since we set the NMI_ENABLE bit while selecting the RTC_INDEX. However, to make clear hat we are disabling NMI and to improve readability (by matching NMI disable/enable), the nmi_disable() call was purposely used. [1] http://wiki.osdev.org/RTC
96 lines
3.3 KiB
C
96 lines
3.3 KiB
C
/*
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* Copyright (C) 2015, Intel Corporation. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* 3. Neither the name of the copyright holder nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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* OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "drivers/legacy_pc/rtc.h"
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#include "drivers/legacy_pc/pic.h"
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#include "drivers/legacy_pc/nmi.h"
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#include "helpers.h"
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#include "interrupt.h"
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#define RTC_INDEX_REGISTER 0x70
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#define RTC_TARGET_REGISTER 0x71
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#define RTC_IRQ 8
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#define RTC_INT PIC_INT(RTC_IRQ)
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static void (*user_callback)(void);
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static void
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rtc_handler()
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{
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user_callback();
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/* Clear Register C otherwise interrupts will not happen again.
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* Register C is automatically cleared when it is read so we do
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* a dummy read to clear it.
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*/
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outb(RTC_INDEX_REGISTER, 0x0C);
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inb(RTC_TARGET_REGISTER);
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/* Issue the End of Interrupt to PIC */
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pic_eoi(RTC_IRQ);
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}
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/*---------------------------------------------------------------------------*/
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/* Initialize the Real Time Clock.
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* @frequency: RTC has very specific values for frequency. They are: 2, 4, 8,
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* 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, and 8192 Hz.
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* value otherwise it will not work properly.
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* @callback: This callback is called every time the RTC IRQ is raised.
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* It is executed in interrupt context.
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*/
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void
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rtc_init(rtc_frequency_t frequency, void (*callback)(void))
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{
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uint8_t reg_a, reg_b;
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user_callback = callback;
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SET_INTERRUPT_HANDLER(RTC_INT, 0, rtc_handler);
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nmi_disable();
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/* Select interrupt period to 7.8125 ms */
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outb(RTC_INDEX_REGISTER, 0x8A);
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reg_a = inb(RTC_TARGET_REGISTER);
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reg_a &= 0xF0;
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reg_a |= frequency;
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outb(RTC_INDEX_REGISTER, 0x8A);
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outb(RTC_TARGET_REGISTER, reg_a);
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/* Enable periodic interrupt */
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outb(RTC_INDEX_REGISTER, 0x8B);
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reg_b = inb(RTC_TARGET_REGISTER);
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outb(RTC_INDEX_REGISTER, 0x8B);
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outb(RTC_TARGET_REGISTER, reg_b | BIT(6));
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nmi_enable();
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pic_unmask_irq(RTC_IRQ);
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}
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