src/arch/aarch64/pl011.c

/*
 * Copyright 2018 The Hafnium Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "hf/dlog.h"

#include "io.h"

/* UART Data Register. */
#define UARTDR 0

/* UART Flag Register. */
#define UARTFR 0x018

/* UART Flag Register bit: transmit fifo is full. */
#define UARTFR_TXFF (1 << 5)

/* UART Flag Register bit: UART is busy. */
#define UARTFR_BUSY (1 << 3)

void arch_putchar(char c)
{
	/* Print a carriage-return as well. */
	if (c == '\n') {
		arch_putchar('\r');
	}

	/* Wait until there is room in the tx buffer. */
	while (io_read(PL011_BASE + UARTFR) & UARTFR_TXFF) {
		/* do nothing */
	}

	dmb();

	/* Write the character out. */
	io_write(PL011_BASE + UARTDR, c);

	dmb();

	/* Wait until the UART is no longer busy. */
	while (io_read_mb(PL011_BASE + UARTFR) & UARTFR_BUSY) {
		/* do nothing */
	}
}