From e240a46965dd14db6e6bdf8974ebb347f3db860b Mon Sep 17 00:00:00 2001 From: Sarah Bessmer Date: Thu, 9 Jan 2014 11:36:31 -0800 Subject: [PATCH] ALSA: ctxfi - Work around emu20k1 glitch to prevent buffered sound data loss Occasionally, on playback stream ringbuffer wraparound, the EMU20K1 hardware will momentarily return 0 instead of the proper current(loop) address. This patch handles that case, fixing the problem of playback position corruption and subsequent loss of buffered sound data, that occurs with some common buffering layout patterns(e.g. multiple simultaneous output streams with differently-sized or non-power-of-2-sized buffers). An alternate means of fixing the problem would be to read the ca register continuously, until two sequential reads return the same value; however, that would be a more invasive change, has performance implications, and isn't necessary unless there are also issues with the value not being updated atomically in regards to individual bits or something similar(which I have not encountered through light testing). I have no EMU20K2 hardware to confirm if the issue is present there, but even if it's not, this change shouldn't break anything that's not already broken. Signed-off-by: Sarah Bessmer Signed-off-by: Takashi Iwai --- sound/pci/ctxfi/ctatc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/sound/pci/ctxfi/ctatc.c b/sound/pci/ctxfi/ctatc.c index b5fa583a239a..eb86829529eb 100644 --- a/sound/pci/ctxfi/ctatc.c +++ b/sound/pci/ctxfi/ctatc.c @@ -435,6 +435,11 @@ atc_pcm_playback_position(struct ct_atc *atc, struct ct_atc_pcm *apcm) return 0; position = src->ops->get_ca(src); + if (position < apcm->vm_block->addr) { + snd_printdd("ctxfi: bad ca - ca=0x%08x, vba=0x%08x, vbs=0x%08x\n", position, apcm->vm_block->addr, apcm->vm_block->size); + position = apcm->vm_block->addr; + } + size = apcm->vm_block->size; max_cisz = src->multi * src->rsc.msr; max_cisz = 128 * (max_cisz < 8 ? max_cisz : 8); -- 2.20.1