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x86: Disable NMI while initializing RTC

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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
This commit is contained in:
Andre Guedes 2015-05-06 15:24:43 -03:00 committed by Jesus Sanchez-Palencia
parent a8849b2909
commit cb0510ebcf
4 changed files with 95 additions and 5 deletions
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2
cpu/x86/Makefile.x86_quarkX1000
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@ -2,6 +2,6 @@ include $(CONTIKI)/cpu/x86/Makefile.x86_common
CONTIKI_CPU_DIRS += drivers/legacy_pc init/legacy_pc
CONTIKI_SOURCEFILES += bootstrap_quarkX1000.S rtc.c pit.c pic.c irq.c
CONTIKI_SOURCEFILES += bootstrap_quarkX1000.S rtc.c pit.c pic.c irq.c nmi.c
LINKERSCRIPT = $(CONTIKI)/cpu/x86/quarkX1000.ld

47
cpu/x86/drivers/legacy_pc/nmi.c Normal file
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@ -0,0 +1,47 @@
/*
* 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 "helpers.h"
#define NMI_ENABLE_PORT 0x70
void
nmi_enable(void)
{
uint8_t value = inb(NMI_ENABLE_PORT);
outb(NMI_ENABLE_PORT, value & ~BIT(8));
}
/*---------------------------------------------------------------------------*/
void
nmi_disable(void)
{
uint8_t value = inb(NMI_ENABLE_PORT);
outb(NMI_ENABLE_PORT, value | BIT(8));
}

38
cpu/x86/drivers/legacy_pc/nmi.h Normal file
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@ -0,0 +1,38 @@
/*
* 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.
*/
#ifndef NMI_H
#define NMI_H
void nmi_enable(void);
void nmi_disable(void);
#endif /* NMI_H */

13
cpu/x86/drivers/legacy_pc/rtc.c
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@ -30,6 +30,7 @@
#include "drivers/legacy_pc/rtc.h"
#include "drivers/legacy_pc/pic.h"
#include "drivers/legacy_pc/nmi.h"
#include "helpers.h"
#include "interrupt.h"
@ -72,19 +73,23 @@ rtc_init(rtc_frequency_t frequency, void (*callback)(void))
SET_INTERRUPT_HANDLER(RTC_INT, 0, rtc_handler);
nmi_disable();
/* Select interrupt period to 7.8125 ms */
outb(RTC_INDEX_REGISTER, 0x0A);
outb(RTC_INDEX_REGISTER, 0x8A);
reg_a = inb(RTC_TARGET_REGISTER);
reg_a &= 0xF0;
reg_a |= frequency;
outb(RTC_INDEX_REGISTER, 0x0A);
outb(RTC_INDEX_REGISTER, 0x8A);
outb(RTC_TARGET_REGISTER, reg_a);
/* Enable periodic interrupt */
outb(RTC_INDEX_REGISTER, 0x0B);
outb(RTC_INDEX_REGISTER, 0x8B);
reg_b = inb(RTC_TARGET_REGISTER);
outb(RTC_INDEX_REGISTER, 0x0B);
outb(RTC_INDEX_REGISTER, 0x8B);
outb(RTC_TARGET_REGISTER, reg_b | BIT(6));
nmi_enable();
pic_unmask_irq(RTC_IRQ);
}