mirror of
https://github.com/RGBCube/serenity
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d9c557d0b4
The Raspberry Pi hardware doesn't support a proper software-initiated shutdown, so this instead uses the watchdog to reboot to a special partition which the firmware interprets as an immediate halt on shutdown. When running under Qemu, this causes the emulator to exit.
47 lines
1.6 KiB
C++
47 lines
1.6 KiB
C++
/*
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* Copyright (c) 2023, Daniel Bertalan <dani@danielbertalan.dev>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <Kernel/Arch/aarch64/RPi/MMIO.h>
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#include <Kernel/Arch/aarch64/RPi/Watchdog.h>
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namespace Kernel::RPi {
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struct WatchdogRegisters {
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u32 rstc;
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u32 rsts;
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u32 wdog;
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};
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constexpr u32 PASSWORD = 0x5a000000;
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constexpr u32 RSTS_PARTITION_MASK = 0xfffffaaa;
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constexpr u32 RSTS_PARTITION_SHUTDOWN = 0x00000555;
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constexpr u32 RSTC_WRCFG_MASK = 0xffffffcf;
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constexpr u32 RSTC_WRCFG_FULL_RESET = 0x00000020;
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Watchdog::Watchdog()
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: m_registers(MMIO::the().peripheral<WatchdogRegisters>(0x10'001c))
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{
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}
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Watchdog& Watchdog::the()
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{
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static Watchdog watchdog;
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return watchdog;
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}
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// This is the same mechanism used by Linux, the ARM Trusted Firmware and U-Boot to trigger a system shutdown.
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// See e.g. https://github.com/ARM-software/arm-trusted-firmware/blob/dcf430656ca8ef964fa55ad9eb81cf838c7837f2/plat/rpi/common/rpi3_pm.c#L231-L249
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void Watchdog::system_shutdown()
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{
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// The Raspberry Pi hardware doesn't support powering off. Setting the reboot target partition to this
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// special value will cause the firmware to halt the CPU and put it in a low power state when the watchdog
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// timer expires. When running under Qemu, this will cause the emulator to exit.
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m_registers->rsts = PASSWORD | (m_registers->rsts & RSTS_PARTITION_MASK) | RSTS_PARTITION_SHUTDOWN;
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// Set the timeout to 10 ticks (~150us).
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m_registers->wdog = PASSWORD | 10;
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// Start the watchdog.
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m_registers->rstc = PASSWORD | (m_registers->rstc & RSTC_WRCFG_MASK) | RSTC_WRCFG_FULL_RESET;
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}
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}
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