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authorClemens Ladisch <clemens@ladisch.de>2010-03-24 09:10:54 +0300
committerTakashi Iwai <tiwai@suse.de>2010-03-24 10:02:11 +0300
commit1c583063a5c769fe2ec604752e383972c69e6d9b (patch)
tree566f530439c23f25b448f7e8c6b576bc3f443fdd
parentfc8aa7b16a5fcfe9c6d0be9bb587f1fcedd9145f (diff)
downloadlinux-1c583063a5c769fe2ec604752e383972c69e6d9b.tar.xz
ALSA: cmipci: work around invalid PCM pointer
When the CMI8738 FRAME2 register is read, the chip sometimes (probably when wrapping around) returns an invalid value that would be outside the programmed DMA buffer. This leads to an inconsistent PCM pointer that is likely to result in an underrun. To work around this, read the register multiple times until we get a valid value; the error state seems to be very short-lived. Signed-off-by: Clemens Ladisch <clemens@ladisch.de> Reported-and-tested-by: Matija Nalis <mnalis-alsadev@voyager.hr> Cc: <stable@kernel.org> Signed-off-by: Takashi Iwai <tiwai@suse.de>
-rw-r--r--sound/pci/cmipci.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/sound/pci/cmipci.c b/sound/pci/cmipci.c
index 1ded64e05643..329968edca9b 100644
--- a/sound/pci/cmipci.c
+++ b/sound/pci/cmipci.c
@@ -941,13 +941,21 @@ static snd_pcm_uframes_t snd_cmipci_pcm_pointer(struct cmipci *cm, struct cmipci
struct snd_pcm_substream *substream)
{
size_t ptr;
- unsigned int reg;
+ unsigned int reg, rem, tries;
+
if (!rec->running)
return 0;
#if 1 // this seems better..
reg = rec->ch ? CM_REG_CH1_FRAME2 : CM_REG_CH0_FRAME2;
- ptr = rec->dma_size - (snd_cmipci_read_w(cm, reg) + 1);
- ptr >>= rec->shift;
+ for (tries = 0; tries < 3; tries++) {
+ rem = snd_cmipci_read_w(cm, reg);
+ if (rem < rec->dma_size)
+ goto ok;
+ }
+ printk(KERN_ERR "cmipci: invalid PCM pointer: %#x\n", rem);
+ return SNDRV_PCM_POS_XRUN;
+ok:
+ ptr = (rec->dma_size - (rem + 1)) >> rec->shift;
#else
reg = rec->ch ? CM_REG_CH1_FRAME1 : CM_REG_CH0_FRAME1;
ptr = snd_cmipci_read(cm, reg) - rec->offset;