From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shine Liu Subject: [PATCH] pcm_lib.c: Fixed inaccurate calculation of hw_ptr_interrupt in snd_pcm_update_hw_ptr_interrupt function Date: Wed, 19 Aug 2009 18:22:19 +0800 Message-ID: <1250677339.3516.17.camel@shinel> Reply-To: shinel@foxmail.com Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from smtpbg64.qq.com (smtpbg64.qq.com [119.147.10.223]) by alsa0.perex.cz (Postfix) with SMTP id 39DF024502 for ; Wed, 19 Aug 2009 12:22:39 +0200 (CEST) List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: alsa-devel-bounces@alsa-project.org Errors-To: alsa-devel-bounces@alsa-project.org To: alsa-devel@alsa-project.org Cc: tiwai@suse.de List-Id: alsa-devel@alsa-project.org There's no restriction on that the runtime->period_size should be the multiplicator of the runtime->buffer_size in current kernel code. So "hw_ptr_interrupt = runtime->hw_ptr_interrupt + runtime->period_size;" is not always the trueth. I've encounter the problem of this bug, the kernel told me "PCM: Unexpected hw_pointer value (stream=0, pos=8, intr_ptr=16384)". The period_size and buffer_size I used was 0x800 and 0x3e80 when the bug occured. Following patch will fix the bug. Signed-off-by: Shine Liu ----------------------------------------------------------------------- --- a/sound/core/pcm_lib.c 2009-08-14 06:43:34.000000000 +0800 +++ b/sound/core/pcm_lib.c 2009-08-19 17:59:00.000000000 +0800 @@ -248,6 +248,12 @@ hw_base = runtime->hw_ptr_base; new_hw_ptr = hw_base + pos; hw_ptr_interrupt = runtime->hw_ptr_interrupt + runtime->period_size; + /* if the period_size is not the multiplicator of the + * buffer_size, the hw_ptr_interrupt calculated above + * may not be correct, should be fixed. + */ + if(hw_ptr_interrupt > hw_base + runtime->buffer_size) + hw_ptr_interrupt = hw_base + runtime->buffer_size; delta = new_hw_ptr - hw_ptr_interrupt; if (hw_ptr_interrupt >= runtime->boundary) { hw_ptr_interrupt -= runtime->boundary;