[ALSA] mpu401: reduce tx loop timeout
Reduce the number of times to check for a non-empty Tx FIFO from 100 to
2 because there is no MPU-401 implementation that needs more than one or
two reads to determine the actual FIFO status.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
diff --git a/sound/drivers/mpu401/mpu401_uart.c b/sound/drivers/mpu401/mpu401_uart.c
index 5993864a..dd6ec42 100644
--- a/sound/drivers/mpu401/mpu401_uart.c
+++ b/sound/drivers/mpu401/mpu401_uart.c
@@ -425,16 +425,17 @@
static void snd_mpu401_uart_output_write(struct snd_mpu401 * mpu)
{
unsigned char byte;
- int max = 256, timeout;
+ int max = 256;
do {
if (snd_rawmidi_transmit_peek(mpu->substream_output,
&byte, 1) == 1) {
- for (timeout = 100; timeout > 0; timeout--) {
- if (snd_mpu401_output_ready(mpu))
- break;
- }
- if (timeout == 0)
+ /*
+ * Try twice because there is hardware that insists on
+ * setting the output busy bit after each write.
+ */
+ if (!snd_mpu401_output_ready(mpu) &&
+ !snd_mpu401_output_ready(mpu))
break; /* Tx FIFO full - try again later */
mpu->write(mpu, byte, MPU401D(mpu));
snd_rawmidi_transmit_ack(mpu->substream_output, 1);