| From 1c583063a5c769fe2ec604752e383972c69e6d9b Mon Sep 17 00:00:00 2001 |
| From: Clemens Ladisch <clemens@ladisch.de> |
| Date: Wed, 24 Mar 2010 07:10:54 +0100 |
| Subject: ALSA: cmipci: work around invalid PCM pointer |
| |
| From: Clemens Ladisch <clemens@ladisch.de> |
| |
| commit 1c583063a5c769fe2ec604752e383972c69e6d9b upstream. |
| |
| 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> |
| Signed-off-by: Takashi Iwai <tiwai@suse.de> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de> |
| |
| --- |
| sound/pci/cmipci.c | 14 +++++++++++--- |
| 1 file changed, 11 insertions(+), 3 deletions(-) |
| |
| --- a/sound/pci/cmipci.c |
| +++ b/sound/pci/cmipci.c |
| @@ -941,13 +941,21 @@ static snd_pcm_uframes_t snd_cmipci_pcm_ |
| 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; |
