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https://github.com/RGBCube/serenity
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84fbab6803
Many code patterns and hardware procedures rely on reliable delay in the microseconds granularity, and since they are using such delays which are valid cases, but should not rely on x86 specific code, we allow to determine in compile time the proper platform-specific code to use to invoke such delays.
119 lines
3.3 KiB
C++
119 lines
3.3 KiB
C++
/*
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* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <AK/Format.h>
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#include <AK/Time.h>
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#include <Kernel/Arch/Delay.h>
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#include <Kernel/CMOS.h>
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#include <Kernel/RTC.h>
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namespace Kernel::RTC {
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static time_t s_boot_time;
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void initialize()
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{
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s_boot_time = now();
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}
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time_t boot_time()
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{
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return s_boot_time;
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}
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static bool update_in_progress()
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{
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return CMOS::read(0x0a) & 0x80;
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}
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static u8 bcd_to_binary(u8 bcd)
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{
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return (bcd & 0x0F) + ((bcd >> 4) * 10);
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}
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static bool try_to_read_registers(unsigned& year, unsigned& month, unsigned& day, unsigned& hour, unsigned& minute, unsigned& second)
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{
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// Note: Let's wait 0.01 seconds until we stop trying to query the RTC CMOS
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size_t time_passed_in_milliseconds = 0;
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bool update_in_progress_ended_successfully = false;
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while (time_passed_in_milliseconds < 100) {
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if (!update_in_progress()) {
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update_in_progress_ended_successfully = true;
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break;
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}
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microseconds_delay(1000);
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time_passed_in_milliseconds++;
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}
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if (!update_in_progress_ended_successfully) {
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year = 1970;
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month = 1;
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day = 1;
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hour = 0;
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minute = 0;
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second = 0;
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return false;
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}
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u8 status_b = CMOS::read(0x0b);
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second = CMOS::read(0x00);
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minute = CMOS::read(0x02);
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hour = CMOS::read(0x04);
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day = CMOS::read(0x07);
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month = CMOS::read(0x08);
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year = CMOS::read(0x09);
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bool is_pm = hour & 0x80;
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if (!(status_b & 0x04)) {
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second = bcd_to_binary(second);
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minute = bcd_to_binary(minute);
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hour = bcd_to_binary(hour & 0x7F);
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day = bcd_to_binary(day);
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month = bcd_to_binary(month);
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year = bcd_to_binary(year);
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}
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if (!(status_b & 0x02)) {
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// In the 12 hour clock, midnight and noon are 12, not 0. Map it to 0.
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hour %= 12;
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if (is_pm)
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hour += 12;
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}
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year += 2000;
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return true;
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}
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time_t now()
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{
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auto check_registers_against_preloaded_values = [](unsigned year, unsigned month, unsigned day, unsigned hour, unsigned minute, unsigned second) {
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unsigned checked_year, checked_month, checked_day, checked_hour, checked_minute, checked_second;
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if (!try_to_read_registers(checked_year, checked_month, checked_day, checked_hour, checked_minute, checked_second))
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return false;
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return checked_year == year && checked_month == month && checked_day == day && checked_hour == hour && checked_minute == minute && checked_second == second;
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};
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unsigned year, month, day, hour, minute, second;
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bool did_read_rtc_successfully = false;
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for (size_t attempt = 0; attempt < 5; attempt++) {
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if (!try_to_read_registers(year, month, day, hour, minute, second))
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break;
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if (check_registers_against_preloaded_values(year, month, day, hour, minute, second)) {
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did_read_rtc_successfully = true;
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break;
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}
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}
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dmesgln("RTC: {} Year: {}, month: {}, day: {}, hour: {}, minute: {}, second: {}", (did_read_rtc_successfully ? "" : "(failed to read)"), year, month, day, hour, minute, second);
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time_t days_since_epoch = years_to_days_since_epoch(year) + day_of_year(year, month, day);
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return ((days_since_epoch * 24 + hour) * 60 + minute) * 60 + second;
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}
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}
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