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authorDavid Henningsson <david.henningsson@canonical.com>2013-04-25 14:32:24 +0200
committerTakashi Iwai <tiwai@suse.de>2013-04-26 07:37:09 +0200
commitfa92dd77ec5623cc0546acb77ee61a0a7ea4f0f0 (patch)
tree4d5b8b0fe47eaf9ab35c74ea7fc530068579eb0b /sound/usb
parent4b417cf01657c8dcd03abb0aa49f3825fede6539 (diff)
downloadlinux-fa92dd77ec5623cc0546acb77ee61a0a7ea4f0f0.tar.bz2
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 <david.henningsson@canonical.com> Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb')
-rw-r--r--sound/usb/clock.c2
1 files changed, 2 insertions, 0 deletions
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);