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https://github.com/enjoy-digital/litex.git
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8aa3fb3eb7
Since ressource usage is low with default depth of 16 (implemented in RAM LUTs) we don't keep old behaviour. Tested successfully with BIOS and flterm.
113 lines
2.2 KiB
C
113 lines
2.2 KiB
C
#include <uart.h>
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#include <irq.h>
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#include <generated/csr.h>
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#include <hw/flags.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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*/
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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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static volatile int tx_level;
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void uart_isr(void)
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{
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unsigned int stat;
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stat = uart_ev_pending_read();
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if(stat & UART_EV_RX) {
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while(!uart_rxempty_read()) {
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rx_buf[rx_produce] = uart_rxtx_read();
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rx_produce = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
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uart_ev_pending_write(UART_EV_RX);
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}
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}
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if(stat & UART_EV_TX) {
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uart_ev_pending_write(UART_EV_TX);
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if(tx_level == 0)
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tx_cts = 1;
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while(tx_level > 0 && !uart_txfull_read()) {
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uart_rxtx_write(tx_buf[tx_consume]);
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tx_consume = (tx_consume + 1) & UART_RINGBUFFER_MASK_TX;
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tx_level--;
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}
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}
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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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if(irq_getie()) {
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while(tx_level == UART_RINGBUFFER_SIZE_TX);
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}
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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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uart_rxtx_write(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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tx_level++;
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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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tx_level = 0;
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uart_ev_pending_write(uart_ev_pending_read());
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uart_ev_enable_write(UART_EV_TX | UART_EV_RX);
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mask = irq_getmask();
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mask |= 1 << UART_INTERRUPT;
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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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