litex/software/libbase/uart.c

111 lines
2.3 KiB
C
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#include <uart.h>
#include <irq.h>
#include <generated/csr.h>
#include <hw/flags.h>
/*
* Buffer sizes must be a power of 2 so that modulos can be computed
* with logical AND.
*/
#define UART_RINGBUFFER_SIZE_RX 128
#define UART_RINGBUFFER_MASK_RX (UART_RINGBUFFER_SIZE_RX-1)
static char rx_buf[UART_RINGBUFFER_SIZE_RX];
static volatile unsigned int rx_produce;
static unsigned int rx_consume;
#define UART_RINGBUFFER_SIZE_TX 128
#define UART_RINGBUFFER_MASK_TX (UART_RINGBUFFER_SIZE_TX-1)
static char tx_buf[UART_RINGBUFFER_SIZE_TX];
static unsigned int tx_produce;
static volatile unsigned int tx_consume;
void uart_isr(void)
{
unsigned int stat, rx_produce_next;
stat = uart_ev_pending_read();
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if(stat & UART_EV_RX) {
while(!uart_rxempty_read()) {
rx_produce_next = (rx_produce + 1) & UART_RINGBUFFER_MASK_RX;
if(rx_produce_next != rx_consume) {
rx_buf[rx_produce] = uart_rxtx_read();
rx_produce = rx_produce_next;
}
uart_ev_pending_write(UART_EV_RX);
}
}
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if(stat & UART_EV_TX) {
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uart_ev_pending_write(UART_EV_TX);
while((tx_consume != tx_produce) && !uart_txfull_read()) {
uart_rxtx_write(tx_buf[tx_consume]);
tx_consume = (tx_consume + 1) & UART_RINGBUFFER_MASK_TX;
}
}
}
/* Do not use in interrupt handlers! */
char uart_read(void)
{
char c;
if(irq_getie()) {
while(rx_consume == rx_produce);
} else if (rx_consume == rx_produce) {
return 0;
}
c = rx_buf[rx_consume];
rx_consume = (rx_consume + 1) & UART_RINGBUFFER_MASK_RX;
return c;
}
int uart_read_nonblock(void)
{
return (rx_consume != rx_produce);
}
void uart_write(char c)
{
unsigned int oldmask;
unsigned int tx_produce_next = (tx_produce + 1) & UART_RINGBUFFER_MASK_TX;
if(irq_getie()) {
while(tx_produce_next == tx_consume);
} else if(tx_produce_next == tx_consume) {
return;
}
oldmask = irq_getmask();
irq_setmask(oldmask & ~(1 << UART_INTERRUPT));
if((tx_consume != tx_produce) || uart_txfull_read()) {
tx_buf[tx_produce] = c;
tx_produce = tx_produce_next;
} else {
uart_rxtx_write(c);
}
irq_setmask(oldmask);
}
void uart_init(void)
{
rx_produce = 0;
rx_consume = 0;
tx_produce = 0;
tx_consume = 0;
uart_ev_pending_write(uart_ev_pending_read());
uart_ev_enable_write(UART_EV_TX | UART_EV_RX);
irq_setmask(irq_getmask() | (1 << UART_INTERRUPT));
}
void uart_sync(void)
{
while(tx_consume != tx_produce);
}