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bsp/atsam: Improve UART / USART tx performance

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Put the next character into the send buffer if the buffer is empty and
not when the last character has been sent out to the line. This improves
the performance slightly.

Before that patch, the receive path was faster than the transmit path.
Therefore a simple echo could drop characters on a busy connection.
With this patch sending and receiving has about the same performance so
that no characters are lost.

Fixes #4611
This commit is contained in:
Christian Mauderer
2021-08-12 10:00:56 +02:00
parent f7a204e3d7
commit fc21b923ba
1 changed files with 5 additions and 4 deletions
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9
bsps/arm/atsam/console/console.c
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@@ -145,8 +145,9 @@ static void atsam_uart_interrupt(void *arg)
}
}
if (ctx->transmitting && (sr & UART_SR_TXEMPTY) != 0) {
while (ctx->transmitting && (sr & UART_SR_TXRDY) != 0) {
rtems_termios_dequeue_characters(tty, 1);
sr = regs->UART_SR;
}
}
#endif
@@ -408,16 +409,16 @@ static void atsam_uart_write(
if (len > 0) {
ctx->transmitting = true;
regs->UART_THR = buf[0];
regs->UART_IER = UART_IDR_TXEMPTY;
regs->UART_IER = UART_IDR_TXRDY;
} else {
ctx->transmitting = false;
regs->UART_IDR = UART_IDR_TXEMPTY;
regs->UART_IDR = UART_IDR_TXRDY;
}
#else
size_t i;
for (i = 0; i < len; ++i) {
while ((regs->UART_SR & UART_SR_TXEMPTY) == 0) {
while ((regs->UART_SR & UART_SR_TXRDY) == 0) {
/* Wait */
}