common/console.c


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/*
 * console.c - the console dprintf writes to. the dtb picks the uart,
 * chosen/stdout-path first, any arm,pl011 node as fallback.
 *
 * Copyright (c) 2008 Travis Geiselbrecht
 * Copyright (c) 2026 Bradley Morgan <brads@mainlining.org>
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files
 * (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge,
 * publish, distribute, sublicense, and/or sell copies of the Software,
 * and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

#include <string.h>
#include <stdio.h>
#include <stdarg.h>
#include <sys/types.h>
#include <stdint.h>
#include <libfdt.h>
#include <printf.h>
#include <debug.h>
#include <reg.h>
#include <drivers/serial/pl011.h>

static uintptr_t tb_uart_base;
static uint32 tb_uart_clock;
static bool tb_uart_ready;

/*
 * read one reg pair out of a node. cells are u32s in the blob, address
 * and size widths come from the parent #address-cells/#size-cells,
 * 2/1 is what every board we care about uses, qemu virt included.
 */
static int tb_read_reg(const void *blob, int node, int index,
		       uintptr_t *base, uint32 *size)
{
	const fdt32_t *prop;
	int len;
	int offset;

	prop = fdt_getprop(blob, node, "reg", &len);
	if (!prop)
		return -1;

	/*
	 * a reg pair here is <addr_hi addr_lo size>, 3 cells, 2 for the
	 * address and 1 for the size. index 0 is the pair we want.
	 */
	offset = index * 3;
	if (offset + 3 > len / 4)
		return -1;

	*base = ((uintptr_t)fdt32_to_cpu(prop[offset]) << 32) |
		fdt32_to_cpu(prop[offset + 1]);
	*size = fdt32_to_cpu(prop[offset + 2]);
	return 0;
}

static int tb_console_from_stdout_path(const void *blob)
{
	const char *path;
	const char *p;
	char buf[32];
	int node;
	int chosen;
	int len;

	chosen = fdt_path_offset(blob, "/chosen");
	if (chosen < 0)
		return -1;

	path = fdt_getprop(blob, chosen, "stdout-path", &len);
	if (!path || len <= 0)
		return -1;

	/* the path can carry :baud after the node, cut it */
	p = strchr(path, ':');
	len = p ? (int)(p - path) : strlen(path);
	if (len >= (int)sizeof(buf))
		len = sizeof(buf) - 1;
	memcpy(buf, path, len);
	buf[len] = 0;

	/* a leading / is a full path, otherwise it's an alias */
	if (buf[0] == '/')
		node = fdt_path_offset(blob, buf);
	else
		node = fdt_path_offset(blob, fdt_get_alias(blob, buf));
	if (node < 0)
		return -1;

	return node;
}

static int tb_console_scan(const void *blob)
{
	const char *compat;
	int node;
	int len;

	fdt_for_each_subnode(node, blob, 0) {
		compat = fdt_getprop(blob, node, "compatible", &len);
		if (!compat)
			continue;
		if (fdt_stringlist_contains(compat, len, "arm,pl011"))
			return node;
	}
	return -1;
}

int tb_console_init(const void *dtb)
{
	const fdt32_t *clk;
	int node;
	uint32 size;
	uint32 baud;
	int len;

	node = tb_console_from_stdout_path(dtb);
	if (node < 0)
		node = tb_console_scan(dtb);
	if (node < 0)
		return -1;

	if (tb_read_reg(dtb, node, 0, &tb_uart_base, &size))
		return -1;

	clk = fdt_getprop(dtb, node, "clock-frequency", &len);
	tb_uart_clock = (clk && len == 4) ? fdt32_to_cpu(*clk) : 24000000;

	{
		const fdt32_t *cs;
		int cslen;

		cs = fdt_getprop(dtb, node, "current-speed", &cslen);
		baud = (cs && cslen == 4) ? fdt32_to_cpu(*cs) : 115200;
	}

	pl011_init(tb_uart_base, tb_uart_clock, baud);
	tb_uart_ready = true;
	return 0;
}

static int tb_console_out(char c, void *state)
{
	if (c == '\n')
		pl011_putc(tb_uart_base, '\r');
	pl011_putc(tb_uart_base, c);
	return 1;
}

int _dprintf(const char *fmt, ...)
{
	va_list ap;
	int ret;

	if (!tb_uart_ready)
		return 0;

	va_start(ap, fmt);
	ret = _dvprintf(fmt, ap);
	va_end(ap);
	return ret;
}

int _dvprintf(const char *fmt, va_list ap)
{
	if (!tb_uart_ready)
		return 0;
	return _printf_engine(tb_console_out, NULL, fmt, ap);
}

void platform_halt(void)
{
	for (;;)
		__asm__ volatile("wfe");
}