From: Clemens Ladisch <clemens@ladisch.de>
Date: Thu, 18 Nov 2010 08:53:07 +0000 (+0100)
Subject: ALSA: pcm: optimize xrun detection in no-period-wakeup mode
X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=47228e48aecdbec423a1275a5e27697d47f1f912;p=openwrt%2Fstaging%2Fblogic.git

ALSA: pcm: optimize xrun detection in no-period-wakeup mode

Add a lightweight condition on top of the xrun checking so that we can
avoid the division when the application is calling the update function
often enough.

Suggested-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index e9debaabf376..fd18c3c6484f 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -380,6 +380,8 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
 		 * the elapsed time to detect xruns.
 		 */
 		jdelta = jiffies - runtime->hw_ptr_jiffies;
+		if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
+			goto no_delta_check;
 		hdelta = jdelta - delta * HZ / runtime->rate;
 		while (hdelta > runtime->hw_ptr_buffer_jiffies / 2 + 1) {
 			delta += runtime->buffer_size;