drivers/uart/src/uart_pl011.c

/*
 * Copyright (c) 2019-2020 Arm Limited. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * 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
 *
 * 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.
 */

/* Basic PL011 UART driver */

#include "uart_config.h"
#include "uart_stdout.h"
#include <stdint.h>
#include <stdio.h>

#define CNTLQ     0x11
#define CNTLS     0x13
#define DEL       0x7F
#define BACKSPACE 0x08
#define CR        0x0D
#define LF        0x0A
#define ESC       0x1B

/*****************************************************************************/
/*  UART Control Register Locations                                          */
/*****************************************************************************/
#define UART0_DR   *((volatile uint32_t *)UART0_BASE)
#define UART0_RSR  *((volatile uint32_t *)(UART0_BASE + 0x04))
#define UART0_ECR  *((volatile uint32_t *)(UART0_BASE + 0x04))
#define UART0_LCRH *((volatile uint32_t *)(UART0_BASE + 0x2C))
#define UART0_LCRM *((volatile uint32_t *)(UART0_BASE + 0x28))
#define UART0_LCRL *((volatile uint32_t *)(UART0_BASE + 0x24))
#define UART0_CR   *((volatile uint32_t *)(UART0_BASE + 0x30))
#define UART0_FR   *((volatile uint32_t *)(UART0_BASE + 0x18))
#define UART0_IIR  *((volatile uint32_t *)(UART0_BASE + 0x1C))
#define UART0_ICR  *((volatile uint32_t *)(UART0_BASE + 0x44))

/*****************************************************************************/
/* Received Status Register - RSR                                            */
/*****************************************************************************/
#define RSR_OVERRUN_ERROR 0x08
#define RSR_BREAK_ERROR   0x04
#define RSR_PARITY_ERROR  0x02
#define RSR_FRAMING_ERROR 0x01

/*****************************************************************************/
/* Line Control High Byte Register - LCRH                                    */
/*****************************************************************************/
#define LCRH_WORD_LENGTH_8 0x60
#define LCRH_WORD_LENGTH_7 0x40
#define LCRH_WORD_LENGTH_6 0x20
#define LCRH_WORD_LENGTH_5 0x00
#define LCRH_FIFO_ENABLED  0x10
#define LCRH_2_STOP_BITS   0x08
#define LCRH_EVEN_PARITY   0x04
#define LCRH_PARITY_ENABLE 0x02
#define LCRH_SEND_BREAK    0x01

/*****************************************************************************/
/* Line Control Medium Byte Register - LCRM                                  */
/* This register specifies the high byte of the Baud rate divisor            */
/*****************************************************************************/
#define LCRM_BAUD_460800 0x00
#define LCRM_BAUD_230400 0x00
#define LCRM_BAUD_115200 0x00
#define LCRM_BAUD_76800  0x00
#define LCRM_BAUD_57600  0x00
#define LCRM_BAUD_38400  0x00
#define LCRM_BAUD_19200  0x00
#define LCRM_BAUD_14400  0x00
#define LCRM_BAUD_9600   0x00
#define LCRM_BAUD_2400   0x01
#define LCRM_BAUD_1200   0x02

/*****************************************************************************/
/* Line Control Low Byte Register - LCRL                                     */
/* This register specifies the low byte of the Baud rate divisor             */
/*****************************************************************************/
#define LCRL_BAUD_460800 0x01
#define LCRL_BAUD_230400 0x03
#define LCRL_BAUD_115200 0x07
#define LCRL_BAUD_76800  0x0B
#define LCRL_BAUD_57600  0x0F
#define LCRL_BAUD_38400  0xC
#define LCRL_BAUD_19200  0x2F
#define LCRL_BAUD_14400  0x3F
#define LCRL_BAUD_9600   0x5F
#define LCRL_BAUD_2400   0x7F
#define LCRL_BAUD_1200   0xFF

/*****************************************************************************/
/* Control Register - CR                                                     */
/*****************************************************************************/
#define CR_LOOP_BACK_EN   0x80
#define CR_TIMEOUT_INT_EN 0x40
#define CR_TX_INT_ENABLE  0x100
#define CR_RX_INT_ENABLE  0x200
#define CR_MODSTAT_INT_EN 0x08
#define CR_UART_ENABLE    0x01

/*****************************************************************************/
/* Flag Register - FR                                                        */
/*****************************************************************************/
#define FR_TX_FIFO_EMPTY  0x80
#define FR_RX_FIFO_FULL   0x40
#define FR_TX_FIFO_FULL   0x20
#define FR_RX_FIFO_EMPTY  0x10
#define FR_BUSY           0x08
#define FR_CARRIER_DETECT 0x04
#define FR_SET_READY      0x02
#define FR_CLEAR_TO_SEND  0x01

/*****************************************************************************/
/* Interrupt Identification Register - IIR                                   */
/*****************************************************************************/
#define IIR_RX_TIME_OUT 0x08
#define IIR_TX          0x04
#define IIR_RX          0x02
#define IIR_MODEM       0x01

void UartStdOutInit(void) {
    // Disable the serial port while setting the baud rate and word length
    UART0_CR = 0;

    // Clear the receive status register
    UART0_ECR = 0;

    // Set the correct baud rate and word length
    UART0_LCRL = LCRL_BAUD_115200;
    UART0_LCRM = LCRM_BAUD_115200;
    UART0_LCRH = LCRH_WORD_LENGTH_8;

    // Explicitly disable FIFO's for char mode
    UART0_LCRH &= ~LCRH_FIFO_ENABLED;

    // Enable UART0 (and RX/TX) without interrupts
    UART0_CR = CR_UART_ENABLE | CR_TX_INT_ENABLE | CR_RX_INT_ENABLE;
}

unsigned char UartPutc(unsigned char ch) {
    if (ch == '\n') {
        (void)UartPutc('\r');
    }
    while (UART0_FR & FR_TX_FIFO_FULL)
        ;
    UART0_DR = ch;

    return ch;
}

unsigned char UartGetc(void) {
    unsigned char c;
    while (UART0_FR & FR_RX_FIFO_EMPTY)
        ;
    c = UART0_DR;
    if (c == '\r') {
        c = '\n';
    }

    return c;
}

// Get line from terminal
unsigned int GetLine(char *lp, unsigned int len) {
    unsigned int cnt = 0;
    char c;

    do {
        c = UartGetc();
        switch (c) {
        case CNTLQ: /* ignore Control S/Q             */
        case CNTLS:
            break;
        case BACKSPACE:
        case DEL:
            if (cnt == 0) {
                break;
            }
            cnt--;          /* decrement count                */
            lp--;           /* and line pointer               */
            UartPutc(0x08); /* echo backspace                 */
            UartPutc(' ');
            UartPutc(0x08);
            fflush(stdout);
            break;
        case ESC:
        case 0:
            *lp = 0; /* ESC - stop editing line        */
            return 0;
        case CR: /* CR - done, stop editing line   */
            *lp = c;
            lp++;  /* increment line pointer         */
            cnt++; /* and count                      */
            c = LF;
            UartPutc(*lp = c); /* echo and store character       */
            fflush(stdout);
            lp++;  /* increment line pointer         */
            cnt++; /* and count                      */
            break;
        default:
            UartPutc(*lp = c); /* echo and store character       */
            fflush(stdout);
            lp++;  /* increment line pointer         */
            cnt++; /* and count                      */
            break;
        }
    } while (cnt < len - 2 && c != LF); /* check limit and CR             */
    *lp = 0;                            /* mark end of string             */
    return 1;
}