kernel/target/arm64/boot-shim/msm8x53-som-uart.c

// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <zircon/compiler.h>
#include <stdint.h>
#include "debug.h"

#define UART_DM_N0_CHARS_FOR_TX             0x0040
#define UART_DM_CR_CMD_RESET_TX_READY       (3 << 8)

#define UART_DM_SR                          0x00A4
#define UART_DM_SR_TXRDY                    (1 << 2)
#define UART_DM_SR_TXEMT                    (1 << 3)

#define UART_DM_TF                          0x0100

#define UARTREG(reg) (*(volatile uint32_t*)(0x078af000 + (reg)))

void uart_pputc(char c) {
    while (!(UARTREG(UART_DM_SR) & UART_DM_SR_TXEMT)) {
        ;
    }
    UARTREG(UART_DM_N0_CHARS_FOR_TX) = UART_DM_CR_CMD_RESET_TX_READY;
    UARTREG(UART_DM_N0_CHARS_FOR_TX) = 1;
    __UNUSED uint32_t foo = UARTREG(UART_DM_N0_CHARS_FOR_TX);

    // wait for TX ready
    while (!(UARTREG(UART_DM_SR) & UART_DM_SR_TXRDY))
        ;

    *((volatile uint32_t*)(0x078af100)) = c;

    // wait for TX ready
    while (!(UARTREG(UART_DM_SR) & UART_DM_SR_TXRDY))
        ;
}