[alsa-devel] [Alsa-devel] xrun problem

[Gao, Jonathan]

Hi,
I am writing a PCM driver on a Soc for 2.6.10 kernel.
The test code I'm using is from alsa-lib-1.0.6rc1/test/pcm.c.
The runtime log gives me like this...
-----------------------------------------------------------------
open callback: 
hw params callback: alloc result = 1, buffer bytes = 4608

/* --------- HW params ------------- */
format = 2,     rate = 44100,   channels= 2,    period_size = 288,
periods = 4,    buffer_size = 1152

prepare callback
/* --------- Runtime Info ---------- */
state = 1 (SNDRV_PCM_STATE_SETUP),      hw_ptr = 0,     appl_ptr = 0,
avail_min = 288
avail_max = 0,  hw_ptr_base = 0,        hw_ptr_interrupt = 0

trigger callback: START

Codec Do Copy:
/* --------- Runtime Info ---------- */
state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 0,     appl_ptr =
1152,        avail_min = 288
avail_max = 0,  hw_ptr_base = 0,        hw_ptr_interrupt = 0

pointer callback: hw pointer: 288 (return value of pointer callback)

Codec Do Copy:
/* --------- Runtime Info ---------- */
state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 288,   appl_ptr =
1152,        avail_min = 288
avail_max = 288,        hw_ptr_base = 0,        hw_ptr_interrupt = 288

pointer callback: hw pointer: 576 (return value of pointer callback)

Codec Do Copy: 
/* --------- Runtime Info ---------- */
state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 576,   appl_ptr =
1152,        avail_min = 288
avail_max = 576,        hw_ptr_base = 0,        hw_ptr_interrupt = 576

pointer callback: hw pointer: 864 (return value of pointer callback)

Codec Do Copy:
/* --------- Runtime Info ---------- */
state = 3 (SNDRV_PCM_STATE_RUNNING),      hw_ptr = 864,   appl_ptr =
1152,        avail_min = 288
avail_max = 864,        hw_ptr_base = 0,        hw_ptr_interrupt = 864

pointer callback: hw pointer: 0  (return value of pointer callback)

trigger callback: STOP
prepare callback
/* --------- Runtime Info ---------- */
state = 4 (SNDRV_PCM_STATE_XRUN),      hw_ptr = 1152,  appl_ptr = 1152,
avail_min = 288
avail_max = 1152,       hw_ptr_base = 1152,     hw_ptr_interrupt = 1152
-----------------------------------------------------------------

The kernel hangs after prepare callback, from  strace, I can see a
endless ioctl(4, ..., ...) repeated.
Does anyone have a few pointers on what is going wrong?

Best Regards,
Jonathan