// CC BY
// code by SASANO Takayoshi

#include "io.h"

#define	COM_PORT	0x3f8			// COM1
#define	COM_CLOCK	1843200			// Hz
#define	COM_SPEED	115200
#define	COM_DIVISOR	(COM_CLOCK / (COM_SPEED * 16))

#define	RHR		(COM_PORT + 0x00)	// r
#define	THR		(COM_PORT + 0x00)	//  w
#define	IER		(COM_PORT + 0x01)	// rw
#define	ISR		(COM_PORT + 0x02)	// r
#define	FCR		(COM_PORT + 0x02)	//  w
#define	LCR		(COM_PORT + 0x03)	// rw
#define	MCR		(COM_PORT + 0x04)	// rw
#define	LSR		(COM_PORT + 0x05)	// r

#define	DLL		(COM_PORT + 0x00)	// rw
#define	DLM		(COM_PORT + 0x01)	// rw

void	serial_out(char c)
{
	while (!(in_b(LSR) & 0x20));		// wait for Tx ready
	out_b(THR, c);
}

char	serial_in(void)
{
	unsigned char	s, c;

	while (1) {
		s = in_b(LSR);			// get status
		if (s & 0x1f) {			// Rx ready
			c = in_b(RHR);		// read from FIFO
			if (!(s & 0x1e)) {	// no error
				return c;
			}
		}
	}

	/* NOTREACHED */
}

void	serial_init(void)
{
	out_b(IER, 0x00);		// disable interrupt
	out_b(LCR, 0x80);		// set divisor
	out_b(DLM, 0xff);		// (avoid divisor = 0)
	out_b(DLL, (COM_DIVISOR >> 0) & 0xff);
	out_b(DLM, (COM_DIVISOR >> 8) & 0xff);
	out_b(LCR, 0x03);		// data 8bit, stop 1bit, non-parity
	out_b(MCR, 0x03);		// RTS#, DTR# assert
	out_b(FCR, 0x07);		// FIFO enable and reset
}