linux/arch/parisc/kernel/pdc_cons.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* 
 *    PDC early console support - use PDC firmware to dump text via boot console
 *
 *    Copyright (C) 2001-2022 Helge Deller <deller@gmx.de>
 */

#include <linux/console.h>
#include <linux/init.h>
#include <linux/serial_core.h>
#include <linux/kgdb.h>
#include <asm/page.h>		/* for PAGE0 */
#include <asm/pdc.h>		/* for iodc_call() proto and friends */

static void pdc_console_write(struct console *co, const char *s, unsigned count)
{
	int i = 0;

	do {
		i += pdc_iodc_print(s + i, count - i);
	} while (i < count);
}

#ifdef CONFIG_KGDB
static int kgdb_pdc_read_char(void)
{
	int c = pdc_iodc_getc();

	return (c <= 0) ? NO_POLL_CHAR : c;
}

static void kgdb_pdc_write_char(u8 chr)
{
	/* no need to print char as it's shown on standard console */
	/* pdc_iodc_print(&chr, 1); */
}

static struct kgdb_io kgdb_pdc_io_ops = {
	.name = "kgdb_pdc",
	.read_char = kgdb_pdc_read_char,
	.write_char = kgdb_pdc_write_char,
};
#endif

static int __init pdc_earlycon_setup(struct earlycon_device *device,
				     const char *opt)
{
	struct console *earlycon_console;

	/* If the console is duplex then copy the COUT parameters to CIN. */
	if (PAGE0->mem_cons.cl_class == CL_DUPLEX)
		memcpy(&PAGE0->mem_kbd, &PAGE0->mem_cons, sizeof(PAGE0->mem_cons));

	earlycon_console = device->con;
	earlycon_console->write = pdc_console_write;
	device->port.iotype = UPIO_MEM32BE;

#ifdef CONFIG_KGDB
	kgdb_register_io_module(&kgdb_pdc_io_ops);
#endif

	return 0;
}

EARLYCON_DECLARE(pdc, pdc_earlycon_setup);