recently,i am tracing the process into the snd_pcm_update_hw_ptr0() and find the statement. i do not understand when the
if (hdelta > runtime->hw_ptr_buffer_jiffies/2) (1)will happen? (2)and the reason? (3)the other question is if the dma interrupt will can enter the snd_pcm_update_hw_ptr0() every time when it ocurrs?
thanks for any suggestion. Best Regards L9jj
=====================code start==============================> if (in_interrupt) { /* we know that one period was processed */
/* delta = "expected next hw_ptr" for in_interrupt != 0 */
delta = runtime->hw_ptr_interrupt + runtime->period_size;
if (delta > new_hw_ptr) {
/* 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;
}
}
<=====================code end============================
-- ------------------------------------ l9jj Regards