[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>

1 files changed, 7 insertions, 6 deletions

diff --git a/sound/drivers/mpu401/mpu401_uart.c b/sound/drivers/mpu401/mpu401_uart.c
index 5993864acbd3..dd6ec4266732 100644
--- a/sound/drivers/mpu401/mpu401_uart.c
+++ b/sound/drivers/mpu401/mpu401_uart.c
@@ -425,16 +425,17 @@ static void snd_mpu401_uart_input_read(struct snd_mpu401 * mpu)
 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);