ALSA: pcm midlevel code - add time check for double interrupt acknowledge
The current code in pcm_lib.c do all checks using only the position
in the ring buffer. Unfortunately, where the interrupts gets delayed or
merged into one, we need another timing source to check when the
buffer size boundary overlaps to avoid the wrong updating of the
ring buffer pointers.
This code uses jiffies to check the right time window without any
performance impact.
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index e23e0e7..a1707cc 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -334,11 +334,15 @@
/* delta = "expected next hw_ptr" for in_interrupt != 0 */
delta = runtime->hw_ptr_interrupt + runtime->period_size;
if (delta > new_hw_ptr) {
- hw_base += runtime->buffer_size;
- if (hw_base >= runtime->boundary)
- hw_base = 0;
- new_hw_ptr = hw_base + pos;
- goto __delta;
+ /* check for double acknowledged interrupts */
+ hdelta = jiffies - runtime->hw_ptr_jiffies;
+ if (hdelta > runtime->hw_ptr_buffer_jiffies/2) {
+ hw_base += runtime->buffer_size;
+ if (hw_base >= runtime->boundary)
+ hw_base = 0;
+ new_hw_ptr = hw_base + pos;
+ goto __delta;
+ }
}
}
/* new_hw_ptr might be lower than old_hw_ptr in case when */
