freebsd ati ixp400 issue

% vmstat -i
interrupt                          total       rate
irq1: atkbd0                          46          0
irq6: fdc0                             2          0
irq17: pcm0                       239098          1 <<<
irq19: ohci0 ohci1+               906922          6
irq20: re0                       5775356         43
irq23: atapci0                    361161          2
cpu0:timer                      18739067        141
irq256: vgapci1                     2702          0
Total                           26024354        197


% grep pcm /var/run/dmesg.boot
pcm0: <ATI IXP 400> mem 0xff6ff400-0xff6ff4ff irq 17 at device 20.5 on pci0
pcm0: <Avance Logic ALC655 AC97 Codec>


% pciconf -lv | grep -A 4 pcm
pcm0@pci0:0:20:5:       class=0x040100 card=0xd0081631 chip=0x43701002 rev=0x01 hdr=0x00
    vendor     = 'ATI Technologies Inc'
    device     = 'IXP SB400 AC'97 Audio Controller'
    class      = multimedia
    subclass   = audio


% cat /dev/sndstat
FreeBSD Audio Driver (newpcm: 64bit 2009061500/amd64)
Installed devices:
pcm0: <ATI IXP 400> at memory 0xff6ff400 irq 17 kld snd_atiixp (1p:1v/1r:1v) default
        snddev flags=0x2e2<AUTOVCHAN,BUSY,MPSAFE,REGISTERED,VPC>
        [pcm0:play:dsp0.p0]: spd 48000, fmt 0x00200010, flags 0x00002100, 0x00000004
        interrupts 29477, underruns 0, feed 29477, ready 0 [b:4096/2048/2|bs:4096/2048/2]
        channel flags=0x2100<BUSY,HAS_VCHAN>
        {userland} -> feeder_mixer(0x00200010) -> {hardware}
        pcm0:play:dsp0.p0[pcm0:virtual:dsp0.vp0]: spd 44100/48000, fmt 0x00200010, flags 0x10000000, 0x00000029
        interrupts 0, underruns 0, feed 0, ready 0 [b:0/0/0|bs:65536/2048/32]
        channel flags=0x10000000<VIRTUAL>
        {userland} -> feeder_root(0x00200010) -> feeder_volume(0x00200010) -> feeder_rate(0x00200010 q:1 44100 -> 48000) -> {hardware}
        [pcm0:record:dsp0.r0]: spd 48000, fmt 0x00200010, flags 0x00002100, 0x00000005
        interrupts 0, overruns 0, feed 0, hfree 4096, sfree 4096 [b:4096/2048/2|bs:4096/2048/2]
        channel flags=0x2100<BUSY,HAS_VCHAN>
        {hardware} -> feeder_root(0x00200010) -> feeder_mixer(0x00200010) -> {userland}
        pcm0:record:dsp0.r0[pcm0:virtual:dsp0.vr0]: spd 8000, fmt 0x00100008, flags 0x10000000, 0x00000000
        interrupts 0, overruns 0, feed 0, hfree 0, sfree 0 [b:0/0/0|bs:0/0/0]
        channel flags=0x10000000<VIRTUAL>
        {hardware} -> feeder_root(0x00000000) -> {userland}

File Versions:
$FreeBSD: release/9.1.0/sys/dev/sound/pci/atiixp.c 216518 2010-12-18 14:21:28Z tijl $
$FreeBSD: release/9.1.0/sys/dev/sound/pcm/buffer.c 233164 2012-03-19 07:24:26Z mav $
$FreeBSD: release/9.1.0/sys/dev/sound/pcm/ac97_patch.c 193640 2009-06-07 19:12:08Z ariff $
$FreeBSD: release/9.1.0/sys/dev/sound/pcm/ac97.c 193640 2009-06-07 19:12:08Z ariff $
$FreeBSD: release/9.1.0/sys/dev/sound/pci/hda/hdacc./dev/sound/pcm/feeder.c 193640 2009-06-07 19:12:08Z ariff $
$FreeBSD: release/9.1.0/sys/dev/sound/pcm/dsp.c 225505 2011-09-12 08:38:21Z avg $
$FreeBSD: release/9.1.0/sys/dev/sound/pcm/channel.c 233164 2012-03-19 07:24:26Z mav $

% kldstat
Id Refs Address            Size     Name
 1   27 0xffffffff80200000 1323388  kernel
 2    1 0xffffffff81524000 1f9a0    geom_eli.ko
 3    2 0xffffffff81544000 2b4a8    crypto.ko
 4    2 0xffffffff81570000 dde0     zlib.ko
 6    1 0xffffffff81612000 3dff     linprocfs.ko
 7    1 0xffffffff81616000 1f417    linux.ko
 8    1 0xffffffff81636000 64a8d    radeon.ko
 9    1 0xffffffff8169b000 139a7    drm.ko
10    1 0xffffffff816af000 2c49     snd_atiixp.ko


% sysctl hw.snd
hw.snd.vpc_reset: 0
hw.snd.vpc_0db: 45
hw.snd.vpc_autoreset: 1
hw.snd.latency_profile: 1
hw.snd.latency: 5
hw.snd.report_soft_matrix: 1
hw.snd.report_soft_formats: 1
hw.snd.compat_linux_mmap: 0
hw.snd.feeder_eq_exact_rate: 0
hw.snd.feeder_eq_presets: PEQ:16000,0.2500,62,0.2500:-9,9,1.0:44100,48000,88200,96000,176400,192000
hw.snd.feeder_rate_quality: 1
hw.snd.feeder_rate_round: 25
hw.snd.feeder_rate_max: 2016000
hw.snd.feeder_rate_min: 1
hw.snd.feeder_rate_polyphase_max: 183040
hw.snd.feeder_rate_presets: 100:8:0.85 100:36:0.92 100:164:0.97
hw.snd.vpc_mixer_bypass: 1
hw.snd.verbose: 4
hw.snd.maxautovchans: 16
hw.snd.default_unit: 0
hw.snd.version: 2009061500/amd64
hw.snd.default_auto: 1


% sysctl dev.pcm
dev.pcm.0.%desc: ATI IXP 400
dev.pcm.0.%driver: pcm
dev.pcm.0.%location: slot=20 function=5 handle=\_SB_.PCI0.AC97
dev.pcm.0.%pnpinfo: vendor=0x1002 device=0x4370 subvendor=0x1631 subdevice=0xd008 class=0x040100
dev.pcm.0.%parent: pci0
dev.pcm.0.eapd: 1
dev.pcm.0.play.vchans: 1
dev.pcm.0.play.vchanmode: fixed
dev.pcm.0.play.vchanrate: 48000
dev.pcm.0.play.vchanformat: s16le:2.0
dev.pcm.0.rec.vchans: 1
dev.pcm.0.rec.vchanmode: fixed
dev.pcm.0.rec.vchanrate: 48000
dev.pcm.0.rec.vchanformat: s16le:2.0
dev.pcm.0.buffersize: 16384
dev.pcm.0.bitperfect: 0
dev.pcm.0.polling: 0

% mixer
Mixer vol      is currently set to 100:100
Mixer pcm      is currently set to 100:100
Mixer speaker  is currently set to 100:100
Mixer line     is currently set to 100:100
Mixer mic      is currently set to 100:100
Mixer cd       is currently set to 100:100
Mixer rec      is currently set to 100:100
Mixer igain    is currently set to 100:100
Mixer ogain    is currently set to 100:100
Mixer line1    is currently set to 100:100
Mixer phin     is currently set to 100:100
Mixer phout    is currently set to 100:100
Recording source: mic