126 lines
2.8 KiB
C
126 lines
2.8 KiB
C
/*
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* Milkymist SoC (Software)
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* Copyright (C) 2007, 2008, 2009, 2010, 2012 Sebastien Bourdeauducq
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 3 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <uart.h>
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#include <irq.h>
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#include <hw/uart.h>
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#include <hw/interrupts.h>
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/*
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* Buffer sizes must be a power of 2 so that modulos can be computed
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* with logical AND.
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* RX functions are written in such a way that they do not require locking.
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* TX functions already implement locking.
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*/
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#define UART_RINGBUFFER_SIZE_RX 128
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#define UART_RINGBUFFER_MASK_RX (UART_RINGBUFFER_SIZE_RX-1)
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static char rx_buf[UART_RINGBUFFER_SIZE_RX];
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static volatile unsigned int rx_produce;
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static volatile unsigned int rx_consume;
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#define UART_RINGBUFFER_SIZE_TX 128
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#define UART_RINGBUFFER_MASK_TX (UART_RINGBUFFER_SIZE_TX-1)
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static char tx_buf[UART_RINGBUFFER_SIZE_TX];
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static unsigned int tx_produce;
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static unsigned int tx_consume;
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static volatile int tx_cts;
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void uart_isr(void)
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{
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unsigned int stat = CSR_UART_EV_PENDING;
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if(stat & UART_EV_RX) {
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rx_buf[rx_produce] = CSR_UART_RXTX;
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rx_produce = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
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}
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if(stat & UART_EV_TX) {
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if(tx_produce != tx_consume) {
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CSR_UART_RXTX = tx_buf[tx_consume];
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tx_consume = (tx_consume + 1) & UART_RINGBUFFER_MASK_TX;
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} else
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tx_cts = 1;
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}
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CSR_UART_EV_PENDING = stat;
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irq_ack(IRQ_UART);
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}
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/* Do not use in interrupt handlers! */
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char uart_read(void)
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{
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char c;
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while(rx_consume == rx_produce);
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c = rx_buf[rx_consume];
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rx_consume = (rx_consume + 1) & UART_RINGBUFFER_MASK_RX;
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return c;
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}
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int uart_read_nonblock(void)
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{
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return (rx_consume != rx_produce);
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}
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void uart_write(char c)
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{
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unsigned int oldmask;
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oldmask = irq_getmask();
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irq_setmask(0);
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if(tx_cts) {
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tx_cts = 0;
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CSR_UART_RXTX = c;
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} else {
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tx_buf[tx_produce] = c;
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tx_produce = (tx_produce + 1) & UART_RINGBUFFER_MASK_TX;
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}
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irq_setmask(oldmask);
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}
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void uart_init(void)
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{
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unsigned int mask;
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rx_produce = 0;
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rx_consume = 0;
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tx_produce = 0;
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tx_consume = 0;
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tx_cts = 1;
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irq_ack(IRQ_UART);
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/* ack any events */
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CSR_UART_EV_PENDING = CSR_UART_EV_PENDING;
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/* enable interrupts */
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CSR_UART_EV_ENABLE = UART_EV_TX | UART_EV_RX;
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mask = irq_getmask();
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mask |= IRQ_UART;
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irq_setmask(mask);
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}
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void uart_sync(void)
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{
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while(!tx_cts);
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}
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