From fa92dd77ec5623cc0546acb77ee61a0a7ea4f0f0 Mon Sep 17 00:00:00 2001 From: David Henningsson Date: Thu, 25 Apr 2013 14:32:24 +0200 Subject: ALSA: usb - Avoid unnecessary sample rate changes on USB 2.0 clock sources The Scarlett 2i2 seems to take almost 500 ms to set the sample rate, even if the clock is currently set to that value. This patch speeds up prepare of the device, by avoiding setting the clock to something it already is. Signed-off-by: David Henningsson Signed-off-by: Takashi Iwai --- sound/usb/clock.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'sound') diff --git a/sound/usb/clock.c b/sound/usb/clock.c index b0ec3643eb62..3a2ce390e278 100644 --- a/sound/usb/clock.c +++ b/sound/usb/clock.c @@ -356,6 +356,8 @@ static int set_sample_rate_v2(struct snd_usb_audio *chip, int iface, return clock; prev_rate = get_sample_rate_v2(chip, iface, fmt->altsetting, clock); + if (prev_rate == rate) + return 0; cs_desc = snd_usb_find_clock_source(chip->ctrl_intf, clock); writeable = uac2_control_is_writeable(cs_desc->bmControls, UAC2_CS_CONTROL_SAM_FREQ - 1); -- cgit v1.2.2