From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [PATCH] pcm_lib.c: Fixed inaccurate calculation of hw_ptr_interrupt in snd_pcm_update_hw_ptr_interrupt function Date: Wed, 19 Aug 2009 12:34:04 +0200 Message-ID: References: <1250677339.3516.17.camel@shinel> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mx2.suse.de (cantor2.suse.de [195.135.220.15]) by alsa0.perex.cz (Postfix) with ESMTP id 160A22452E for ; Wed, 19 Aug 2009 12:34:05 +0200 (CEST) In-Reply-To: <1250677339.3516.17.camel@shinel> 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: shinel@foxmail.com Cc: alsa-devel@alsa-project.org List-Id: alsa-devel@alsa-project.org At Wed, 19 Aug 2009 18:22:19 +0800, Shine Liu wrote: > > 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. The hw_ptr_interrupt is the expected position where the current irq is issued. So, the current code should be correct -- it's simply increased in the size of period_size. > 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. Does the problem happen with the latest driver code (as found in sound git tree or alsa-driver-snapshot)? If yes, we'd need more further analysis, e.g. by enabling some xrun_debug flags. thanks, Takashi > 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; > > >