ns8250: Fix sense of LSR_TEMT FCR check

When flushing the UART, we need to drain manually if LSR_TEMT is *not* asserted, aka. if the transmit FIFO is not empty. Reported by: void <[email protected]> Fixes: c4b68e7 "ns8250: Check if flush via FCR succeeded" Differential Revision: https://reviews.freebsd.org/D37185
freebsd · Oct 28, 2022 · 5ad8c32 · 5ad8c32
1 parent ba9f71d
commit 5ad8c32
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/sys/dev/uart/uart_dev_ns8250.c b/sys/dev/uart/uart_dev_ns8250.c
@@ -232,7 +232,7 @@ ns8250_flush(struct uart_bas *bas, int what)
 	 * https://github.com/rust-vmm/vm-superio/issues/83
 	 */
 	lsr = uart_getreg(bas, REG_LSR);
-	if ((lsr & LSR_TEMT) && (what & UART_FLUSH_TRANSMITTER))
+	if (((lsr & LSR_TEMT) == 0) && (what & UART_FLUSH_TRANSMITTER))
 		drain |= UART_DRAIN_TRANSMITTER;
 	if ((lsr & LSR_RXRDY) && (what & UART_FLUSH_RECEIVER))
 		drain |= UART_DRAIN_RECEIVER;