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>

1 files changed, 7 insertions, 0 deletions

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 63d088f2265f..a2a792c18c40 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -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? "