chancel.liu at nxp.com, shengjiu.wang at nxp.com

[Shengjiu Wang]

Hi Takashi Iwai, Jaroslav Kysela

    We encountered an issue in the pcm_dsnoop use case, could you please
help to have a look?

    *Issue description:*
    With two instances for dsnoop type device running in parallel, after
suspend/resume,  one of the instances will be hung in memcpy because the
very large copy size is obtained.

#3 0x0000ffffa78d5098 in snd_pcm_dsnoop_sync_ptr (pcm=0xaaab06563da0)
at pcm_dsnoop.c:158
dsnoop = 0xaaab06563c20
slave_hw_ptr = 64
old_slave_hw_ptr = 533120
avail = *187651522444320*

  * Reason analysis: *
   The root cause that I analysis is that after suspend/resume,  one
instance will get the SND_PCM_STATE_SUSPENDED state from slave pcm device,
  then it will do snd_pcm_prepare() and snd_pcm_start(),  which will reset
the dsnoop->slave_hw_ptr and the hw_ptr of slave pcm device,  then the
state of this instance is correct.  But another instance may not get
the SND_PCM_STATE_SUSPENDED state from slave pcm device because slave
device may have been recovered by first instance,  so
the dsnoop->slave_hw_ptr is not reset.  but because hw_ptr of slave pcm
device has been reset,  so there will be a very large "avail" size.

   *Solution:*
   I didn't come up with a fix for this issue,  seems there is no easy way
to let another instance know this case and reset the
dsnoop->slave_hw_ptr,  could you please help?

Best regards
Wang shengjiu