code/fe310/metal/metal.c


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#include <sys/cdefs.h>

#include "encoding.h"
#include "platform.h"
#include "prci_driver.h"

extern void eos_trap_entry();

static void uart_init(size_t baud_rate) {
    GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
    GPIO_REG(GPIO_IOF_EN) |= IOF0_UART0_MASK;
    UART0_REG(UART_REG_DIV) = PRCI_get_cpu_freq() / baud_rate - 1;
    UART0_REG(UART_REG_TXCTRL) |= UART_TXEN;
    UART0_REG(UART_REG_RXCTRL) |= UART_RXEN;
}

__attribute__((constructor))
void metal_init(void) {
    SPI0_REG(SPI_REG_SCKDIV) = 8;

    PRCI_use_default_clocks();
    PRCI_use_pll(PLL_REFSEL_HFXOSC, 0, 1, 31, 1, -1, -1, -1);
    uart_init(115200);

    write_csr(mtvec, &eos_trap_entry);
    if (read_csr(misa) & (1 << ('F' - 'A'))) { // if F extension is present
        write_csr(mstatus, MSTATUS_FS); // allow FPU instructions without trapping
        write_csr(fcsr, 0); // initialize rounding mode, undefined at reset
    }
}

__attribute__((section(".init")))
void __metal_synchronize_harts() {
}