// SPDX-License-Identifier: GPL-2.0
/*
 * Serial port routines for use during early boot reporting. This code is
 * included from both the compressed kernel and the regular kernel.
 */
#include "boot.h"

#define DEFAULT_SERIAL_PORT 0x3f8 /* ttyS0 */

#define DLAB            0x80

#define TXR             0       /*  Transmit register (WRITE) */
#define RXR             0       /*  Receive register  (READ)  */
#define IER             1       /*  Interrupt Enable          */
#define IIR             2       /*  Interrupt ID              */
#define FCR             2       /*  FIFO control              */
#define LCR             3       /*  Line control              */
#define MCR             4       /*  Modem control             */
#define LSR             5       /*  Line Status               */
#define MSR             6       /*  Modem Status              */
#define DLL             0       /*  Divisor Latch Low         */
#define DLH             1       /*  Divisor latch High        */

#define DEFAULT_BAUD 9600

static void early_serial_init(int port, int baud)
{
        unsigned char c;
        unsigned divisor;

        outb(0x3, port + LCR);  /* 8n1 */
        outb(0, port + IER);    /* no interrupt */
        outb(0, port + FCR);    /* no fifo */
        outb(0x3, port + MCR);  /* DTR + RTS */

        divisor = 115200 / baud;
        c = inb(port + LCR);
        outb(c | DLAB, port + LCR);
        outb(divisor & 0xff, port + DLL);
        outb((divisor >> 8) & 0xff, port + DLH);
        outb(c & ~DLAB, port + LCR);

        early_serial_base = port;
}

static void parse_earlyprintk(void)
{
        int baud = DEFAULT_BAUD;
        char arg[32];
        int pos = 0;
        int port = 0;

        if (cmdline_find_option("earlyprintk", arg, sizeof(arg)) > 0) {
                char *e;

                if (!strncmp(arg, "serial", 6)) {
                        port = DEFAULT_SERIAL_PORT;
                        pos += 6;
                }

                if (arg[pos] == ',')
                        pos++;

                /*
                 * make sure we have
                 *      "serial,0x3f8,115200"
                 *      "serial,ttyS0,115200"
                 *      "ttyS0,115200"
                 */
                if (pos == 7 && !strncmp(arg + pos, "0x", 2)) {
                        port = simple_strtoull(arg + pos, &e, 16);
                        if (port == 0 || arg + pos == e)
                                port = DEFAULT_SERIAL_PORT;
                        else
                                pos = e - arg;
                } else if (!strncmp(arg + pos, "ttyS", 4)) {
                        static const int bases[] = { 0x3f8, 0x2f8 };
                        int idx = 0;

                        /* += strlen("ttyS"); */
                        pos += 4;

                        if (arg[pos++] == '1')
                                idx = 1;

                        port = bases[idx];
                }

                if (arg[pos] == ',')
                        pos++;

                baud = simple_strtoull(arg + pos, &e, 0);
                if (baud == 0 || arg + pos == e)
                        baud = DEFAULT_BAUD;
        }

        if (port)
                early_serial_init(port, baud);
}

#define BASE_BAUD (1843200/16)
static unsigned int probe_baud(int port)
{
        unsigned char lcr, dll, dlh;
        unsigned int quot;

        lcr = inb(port + LCR);
        outb(lcr | DLAB, port + LCR);
        dll = inb(port + DLL);
        dlh = inb(port + DLH);
        outb(lcr, port + LCR);
        quot = (dlh << 8) | dll;

        return BASE_BAUD / quot;
}

static void parse_console_uart8250(void)
{
        char optstr[64], *options;
        int baud = DEFAULT_BAUD;
        int port = 0;

        /*
         * console=uart8250,io,0x3f8,115200n8
         * need to make sure it is last one console !
         */
        if (cmdline_find_option("console", optstr, sizeof(optstr)) <= 0)
                return;

        options = optstr;

        if (!strncmp(options, "uart8250,io,", 12))
                port = simple_strtoull(options + 12, &options, 0);
        else if (!strncmp(options, "uart,io,", 8))
                port = simple_strtoull(options + 8, &options, 0);
        else
                return;

        if (options && (options[0] == ','))
                baud = simple_strtoull(options + 1, &options, 0);
        else
                baud = probe_baud(port);

        if (port)
                early_serial_init(port, baud);
}

void console_init(void)
{
        parse_earlyprintk();

        if (!early_serial_base)
                parse_console_uart8250();
}