From 57dd5414a087991d427067b32dc3324af61b1c8b Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Fri, 29 Apr 2016 11:49:04 +0200 Subject: ALSA: usb-audio: Limit retrying sample rate reads There are many USB audio devices with buggy firmware that don't react with the sample rate reading properly. This often results in the flood of error messages and slowing down the operation. The sample rate read back is basically only for confirming the sample rate setup, and it's not critically important. As a compromise, in this patch, we stop the sample rate read back once when the device gives errors more than tolerance (twice, as of now). This should improve most of error cases while we still can catch the firmware bugginess. Signed-off-by: Takashi Iwai --- sound/usb/clock.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'sound/usb/clock.c') diff --git a/sound/usb/clock.c b/sound/usb/clock.c index 7ccbcaf6a147..26dd5f20f149 100644 --- a/sound/usb/clock.c +++ b/sound/usb/clock.c @@ -309,6 +309,9 @@ static int set_sample_rate_v1(struct snd_usb_audio *chip, int iface, * support reading */ if (snd_usb_get_sample_rate_quirk(chip)) return 0; + /* the firmware is likely buggy, don't repeat to fail too many times */ + if (chip->sample_rate_read_error > 2) + return 0; if ((err = snd_usb_ctl_msg(dev, usb_rcvctrlpipe(dev, 0), UAC_GET_CUR, USB_TYPE_CLASS | USB_RECIP_ENDPOINT | USB_DIR_IN, @@ -316,6 +319,7 @@ static int set_sample_rate_v1(struct snd_usb_audio *chip, int iface, data, sizeof(data))) < 0) { dev_err(&dev->dev, "%d:%d: cannot get freq at ep %#x\n", iface, fmt->altsetting, ep); + chip->sample_rate_read_error++; return 0; /* some devices don't support reading */ } -- cgit 1.4.1