ALSA: pcm: Modify double acknowledged interrupts check condition
authorKoro Chen <koro.chen@mediatek.com>
Wed, 13 May 2015 14:39:03 +0000 (22:39 +0800)
committerTakashi Iwai <tiwai@suse.de>
Tue, 19 May 2015 07:32:29 +0000 (09:32 +0200)
commit13a988396cab68e6c6afd33e461a9e52ce23ff63
tree546fd85f5d70daee71117ae79a1a7cb556ac6881
parent5a6cc82171dba297ceab49cda47f2bf5616f87b3
ALSA: pcm: Modify double acknowledged interrupts check condition

Currently in snd_pcm_update_hw_ptr0 during interrupt,
we consider there were double acknowledged interrupts when:
1. HW reported pointer is smaller than expected, and
2. Time from last update time (hdelta) is over half a buffer time.

However, when HW reported pointer is only a few bytes smaller than
expected, and when hdelta is just a little larger than half a buffer time
(e.g. ping-pong buffer), it wrongly treats this IRQ as double acknowledged.

The condition #2 uses jiffies, but jiffies is not high resolution
since it is integer. We should consider jiffies inaccuracy.

Signed-off-by: Koro Chen <koro.chen@mediatek.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
sound/core/pcm_lib.c