[alsa-devel] [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 aotos@fastmail.fm Cc: Takashi Iwai tiwai@suse.de --- --- linux-3.10.25/sound/pci/ctxfi/ctatc.c.orig 2014-01-09 10:12:00.000000000 -0800 +++ linux-3.10.25/sound/pci/ctxfi/ctatc.c 2014-01-09 10:32:42.000000000 -0800 @@ -433,10 +433,15 @@ atc_pcm_playback_position(struct ct_atc
if (!src) 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);
return (position + size - max_cisz - apcm->vm_block->addr) % size;
At Thu, 9 Jan 2014 11:36:31 -0800, Sarah Bessmer wrote:
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 aotos@fastmail.fm Cc: Takashi Iwai tiwai@suse.de
Thanks, applied with a space fix.
Takashi
--- linux-3.10.25/sound/pci/ctxfi/ctatc.c.orig 2014-01-09 10:12:00.000000000 -0800 +++ linux-3.10.25/sound/pci/ctxfi/ctatc.c 2014-01-09 10:32:42.000000000 -0800 @@ -433,10 +433,15 @@ atc_pcm_playback_position(struct ct_atc
if (!src) 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);
return (position + size - max_cisz - apcm->vm_block->addr) % size;
Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
participants (2)
-
Sarah Bessmer -
Takashi Iwai