1 files changed, 12 insertions, 13 deletions

diff --git a/sound/drivers/mpu401/mpu401_uart.c b/sound/drivers/mpu401/mpu401_uart.c
index 5993864acbd3..2af09996a3d0 100644
--- a/sound/drivers/mpu401/mpu401_uart.c
+++ b/sound/drivers/mpu401/mpu401_uart.c
@@ -49,12 +49,10 @@ static void snd_mpu401_uart_output_write(struct snd_mpu401 * mpu);
 
  */
 
-#define snd_mpu401_input_avail(mpu)	(!(mpu->read(mpu, MPU401C(mpu)) & 0x80))
-#define snd_mpu401_output_ready(mpu)	(!(mpu->read(mpu, MPU401C(mpu)) & 0x40))
-
-#define MPU401_RESET		0xff
-#define MPU401_ENTER_UART	0x3f
-#define MPU401_ACK		0xfe
+#define snd_mpu401_input_avail(mpu) \
+	(!(mpu->read(mpu, MPU401C(mpu)) & MPU401_RX_EMPTY))
+#define snd_mpu401_output_ready(mpu) \
+	(!(mpu->read(mpu, MPU401C(mpu)) & MPU401_TX_FULL))
 
 /* Build in lowlevel io */
 static void mpu401_write_port(struct snd_mpu401 *mpu, unsigned char data,
@@ -245,7 +243,7 @@ static int snd_mpu401_uart_cmd(struct snd_mpu401 * mpu, unsigned char cmd,
 #endif
 	}
 	mpu->write(mpu, cmd, MPU401C(mpu));
-	if (ack) {
+	if (ack && !(mpu->info_flags & MPU401_INFO_NO_ACK)) {
 		ok = 0;
 		timeout = 10000;
 		while (!ok && timeout-- > 0) {
@@ -425,16 +423,17 @@ 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);