From e64e94df9916a1db6c85a3677e20926c99a1d0b3 Mon Sep 17 00:00:00 2001 From: Chris Rorvick Date: Tue, 10 Feb 2015 23:03:13 -0600 Subject: [PATCH] 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 Signed-off-by: Takashi Iwai --- sound/usb/line6/driver.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c index 626b0c3..2f9b74e 100644 --- a/sound/usb/line6/driver.c +++ b/sound/usb/line6/driver.c @@ -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 | -- 2.7.4