[047/116] ALSA: cmipci: work around invalid PCM pointer
in [Kernel]
|
Prev: [031/116] sched: Mark boot-cpu active before smp_init()
Next: [039/116] virtio: fix out of range array access
From: Greg KH on 30 Mar 2010 20:20 2.6.32-stable review patch. If anyone has any objections, please let us know. ------------------ From: Clemens Ladisch <clemens(a)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(a)ladisch.de> Reported-and-tested-by: Matija Nalis <mnalis-alsadev(a)voyager.hr> Signed-off-by: Takashi Iwai <tiwai(a)suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh(a)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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |