67 lines
1.5 KiB
C++
67 lines
1.5 KiB
C++
#include <cstdint>
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#include "bios.h"
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#include "interrupts.h"
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namespace {
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constexpr uint32_t kMstatusMieMask = 1 << 3;
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constexpr uint32_t kMieExternalInterruptMask = 1 << 11;
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constexpr uint32_t kExternalInterruptCause = 0x0b;
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constexpr uint32_t kInterruptCauseMask = 0xff;
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Isr external_handler = nullptr;
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__attribute__((interrupt))
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void TrapHandler() {
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uint32_t mcause;
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uint32_t mip;
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asm volatile("csrr %0, mcause" : "=r"(mcause));
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asm volatile("csrr %0, mip" : "=r"(mip));
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// check for external interrupt
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if ((mcause & kInterruptCauseMask) == kExternalInterruptCause) {
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if (external_handler != nullptr) {
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external_handler();
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}
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mip &= ~(kMieExternalInterruptMask);
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asm volatile("csrw mip, %0" :: "r"(mip));
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} else {
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BiosWozmon();
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}
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}
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} // namespace
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void SetExternalInterruptHandler(Isr handler) {
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external_handler = handler;
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}
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void EnableExternalInterrupts() {
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uint32_t mie;
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Isr trap = TrapHandler;
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asm volatile("csrr %0, mie" : "=r"(mie));
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asm volatile("csrw mtvec, %0" :: "r"(trap));
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mie |= kMieExternalInterruptMask;
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asm volatile("csrw mie, %0" :: "r"(mie));
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}
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bool EnableInterrupts(bool on) {
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uint32_t mstatus;
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bool was_on;
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asm volatile("csrr %0, mstatus" : "=r"(mstatus));
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was_on = (mstatus & kMstatusMieMask) > 0;
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if (on) {
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mstatus |= kMstatusMieMask;
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} else {
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mstatus &= ~kMstatusMieMask;
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}
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asm volatile("csrw mstatus, %0" :: "r"(mstatus));
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return was_on;
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}
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