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
48 lines
1.9 KiB
C
48 lines
1.9 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 "helpers.h"
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#define NMI_ENABLE_PORT 0x70
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void
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nmi_enable(void)
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{
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uint8_t value = inb(NMI_ENABLE_PORT);
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outb(NMI_ENABLE_PORT, value & ~BIT(8));
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}
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/*---------------------------------------------------------------------------*/
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void
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nmi_disable(void)
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{
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uint8_t value = inb(NMI_ENABLE_PORT);
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outb(NMI_ENABLE_PORT, value | BIT(8));
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}
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