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ALSA: line6: Add delay before reading status 

The device indicates the result of a read/write operation by making the
status available on a subsequent request from the driver.  This is not
ready immediately, though, so the driver is currently slamming the
device with hundreds of pointless requests before getting the expected
response.  Add a two millisecond delay before each attempt.  This is
approximately the behavior observed with version 4.2.7.1 of the Windows
driver.

Signed-off-by: Chris Rorvick <chris@rorvick.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
hifive-unleashed-5.1
Chris Rorvick 2015-02-10 23:03:13 -06:00 committed by Takashi Iwai
parent 1b006996b6
commit e64e94df99
1 changed files with 6 additions and 0 deletions
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6
sound/usb/line6/driver.c
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@ -296,6 +296,8 @@ static void line6_data_received(struct urb *urb)
line6_start_listen(line6);
}
#define LINE6_READ_WRITE_STATUS_DELAY 2 /* milliseconds */
/*
Read data from device.
*/
@ -319,6 +321,8 @@ int line6_read_data(struct usb_line6 *line6, int address, void *data,
/* Wait for data length. We'll get 0xff until length arrives. */
do {
mdelay(LINE6_READ_WRITE_STATUS_DELAY);
ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0), 0x67,
USB_TYPE_VENDOR | USB_RECIP_DEVICE |
USB_DIR_IN,
@ -376,6 +380,8 @@ int line6_write_data(struct usb_line6 *line6, int address, void *data,
}
do {
mdelay(LINE6_READ_WRITE_STATUS_DELAY);
ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0),
0x67,
USB_TYPE_VENDOR | USB_RECIP_DEVICE |