Fábio Coutada
173b2c3330
- Add kernel/arch/arm/boot.S with ARMv7 assembly entry, stack setup, BSS clear - Add kernel/arch/arm/linker.ld for QEMU virt memory layout (load at 0x40000000) - Add kernel/arch/arm/uart.c/uart.h for PL011 serial output - Add kernel/kernel.c with kernel_main() idle loop - Add kernel/Makefile for arm-none-eabi-gcc cross-compile and QEMU launch - Add kernel/README.md with build/run instructions - Ignore kernel build artifacts in .gitignore
32 lines
677 B
C
32 lines
677 B
C
/*
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* PL011 UART driver for QEMU ARM virt machine.
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*
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* The virt machine exposes a PL011 UART at 0x09000000.
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*/
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#include "uart.h"
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#define UART0_BASE 0x09000000U
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#define UART_DR (*(volatile unsigned int *)(UART0_BASE + 0x00U))
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#define UART_FR (*(volatile unsigned int *)(UART0_BASE + 0x18U))
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#define UART_FR_TXFF (1U << 5)
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void uart_init(void)
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{
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/* QEMU initializes the UART for us. */
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}
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void uart_putc(char c)
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{
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while ((UART_FR & UART_FR_TXFF) != 0U) {
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/* Wait until the transmit FIFO is not full. */
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}
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UART_DR = (unsigned int)c;
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}
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void uart_puts(const char *s)
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{
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while (*s != '\0') {
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uart_putc(*s++);
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}
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}
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