forked from xamidev/pepperOS
106 lines
2.5 KiB
C
106 lines
2.5 KiB
C
/*
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* @author xamidev <xamidev@riseup.net>
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* @brief Debug serial driver
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* @license GPL-3.0-only
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*/
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#include <kernel.h>
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#include "serial.h"
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extern struct init_status init;
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/*
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* outb - Writes a byte to a CPU port
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* @port: CPU port to write to
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* @data: Byte to write
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*
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* Writes a single byte to the serial interface.
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*/
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void outb(int port, unsigned char data)
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{
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__asm__ __volatile__("outb %%al, %%dx" :: "a" (data),"d" (port));
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}
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/*
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* inb - Gets a byte in through a CPU port
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* @port: The CPU port to get a byte from
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*
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* Return:
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* <data> - byte got from port
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*/
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unsigned char inb(int port)
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{
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unsigned char data = 0;
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__asm__ __volatile__("inb %%dx, %%al" : "=a" (data) : "d" (port));
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return data;
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}
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/*
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* serial_init - Initializes serial interface
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*
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* Return:
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* %-EIO - Input/output error
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* %0 - Success
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*/
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int serial_init()
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{
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outb(PORT + 1, 0x00); // Disable all interrupts
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outb(PORT + 3, 0x80); // Enable DLAB (set baud rate divisor)
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outb(PORT + 0, 0x03); // Set divisor to 3 (lo byte) 38400 baud
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outb(PORT + 1, 0x00); // (hi byte)
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outb(PORT + 3, 0x03); // 8 bits, no parity, one stop bit
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outb(PORT + 2, 0xC7); // Enable FIFO, clear them, with 14-byte threshold
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outb(PORT + 4, 0x0B); // IRQs enabled, RTS/DSR set
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outb(PORT + 4, 0x1E); // Set in loopback mode, test the serial chip
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outb(PORT + 0, 0xAE); // Test serial chip (send byte 0xAE and check if serial returns same byte)
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if (inb(PORT) != 0xAE) {
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return -EIO;
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}
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// Set normal operation mode
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outb(PORT + 4, 0x0F);
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init.serial = true;
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DEBUG("*** Welcome to PepperOS! (built @ %s %s) ***", __DATE__, __TIME__);
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return 0;
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}
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/*
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* is_transmit_empty - Check if the serial transmit register is empty
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*
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* Return: Non-zero if the transmit register is empty and a new
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* byte can be written to the serial port, 0 otherwise.
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*/
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static int is_transmit_empty()
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{
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return inb(PORT + 5) & 0x20;
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}
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/*
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* skputc - Serial kernel putchar
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* @c: character to write
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*
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* Writes a single character to the serial interface.
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*/
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void skputc(char c)
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{
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// TODO: Spinlock here (serial access)
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while (!is_transmit_empty()); // wait for free spot
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outb(PORT, c);
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}
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/*
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* skputs - Serial kernel puts
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* @str: Message to write
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*
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* Writes a non-formatted string to serial output.
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*/
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void skputs(const char* str)
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{
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unsigned int i=0;
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while (str[i]) {
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skputc(str[i]);
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i++;
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}
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} |