From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sarah Bessmer Subject: [PATCH] ALSA: ctxfi - Work around emu20k1 glitch to prevent buffered sound data loss Date: Thu, 9 Jan 2014 11:36:31 -0800 Message-ID: <20140109113631.3e941cb1@willow> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from out3-smtp.messagingengine.com (out3-smtp.messagingengine.com [66.111.4.27]) by alsa0.perex.cz (Postfix) with ESMTP id 5D69E2652E8 for ; Thu, 9 Jan 2014 20:36:38 +0100 (CET) List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org Cc: Takashi Iwai List-Id: alsa-devel@alsa-project.org 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 Cc: Takashi Iwai --- --- 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;