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ALSA: pcm core - Avoid jiffies check for devices with BATCH flag 

The hardware devices with SNDRV_PCM_INFO_BATCH flag can't give the
precise current position.  And such hardwares have often big FIFO
in addition to the ring buffer, and it screws up the jiffies check
in pcm_lib.c.

This patch adds a simple check of info flag so that the driver skips
the jiffies check in snd_pcm_period_elapsed() when BATCH flag is set.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2009-04-28 12:07:08 +02:00
parent 2008f137e9
commit 3e5b50165f
1 changed files with 7 additions and 0 deletions
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7
sound/core/pcm_lib.c
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@ -249,6 +249,12 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
new_hw_ptr = hw_base + pos;
}
}
/* Skip the jiffies check for hardwares with BATCH flag.
* Such hardware usually just increases the position at each IRQ,
* thus it can't give any strange position.
*/
if (runtime->hw.info & SNDRV_PCM_INFO_BATCH)
goto no_jiffies_check;
hdelta = new_hw_ptr - old_hw_ptr;
jdelta = jiffies - runtime->hw_ptr_jiffies;
if (((hdelta * HZ) / runtime->rate) > jdelta + HZ/100) {
@ -272,6 +278,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
hw_base -= hw_base % runtime->buffer_size;
delta = 0;
}
no_jiffies_check:
if (delta > runtime->period_size + runtime->period_size / 2) {
hw_ptr_error(substream,
"Lost interrupts? "