From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.suse.de (cantor.suse.de [195.135.220.2]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx1.suse.de", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTP id 1372ADDF2B for ; Fri, 9 Feb 2007 01:07:53 +1100 (EST) Date: Thu, 08 Feb 2007 15:07:44 +0100 Message-ID: From: Takashi Iwai To: Johannes Berg Subject: Re: [PATCH] aoa i2sbus: Stop Apple i2s DMA gracefully In-Reply-To: <1170940357.4385.46.camel@johannes.berg> References: <17732.11228.441627.300383@cargo.ozlabs.ibm.com> <1170940357.4385.46.camel@johannes.berg> MIME-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Cc: linuxppc-dev list , alsa-devel@alsa-project.org, Paul Mackerras , benjamin@sipsolutions.net List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , At Thu, 08 Feb 2007 14:12:37 +0100, Johannes Berg wrote: > > From: Paul Mackerras > > This fixes the problem of getting extra bytes inserted at the > beginning of a recording when using the Apple i2s interface and DBDMA > controller. It turns out that we can't just abort the DMA; we have to > let it stop at the end of a command, and then wait for the S7 bit to > be set before turning off the DBDMA controller. Doing that for > playback doesn't seem to be necessary, but doesn't hurt either. > > We use the technique used by the Darwin driver: make each transfer > command branch to a stop command if the S0 status bit is set. Thus we > can ask the DMA controller to stop at the end of the current command > by setting S0. > > The interrupt routine now looks at and clears the status word of the > DBDMA command ring. This is necessary so it can know when the DBDMA > controller has seen that S0 is set, and so when it should look for the > DBDMA controller being stopped and S7 being set. This also ended up > simplifying the calculation in i2sbus_pcm_pointer. > > Tested on a 15 inch albook. > > Signed-off-by: Paul Mackerras > > I modified this patch and added the suspend/resume bits to it to get my > powermac into a decent state when playing sound across suspend to disk > that has a different bitrate from what the firmware programs the > hardware to. > > I also added the SNDRV_PCM_INFO_JOINT_DUPLEX flag because it seemed the > right thing to do and I was looking at the info stuff. > > Signed-off-by: Johannes Berg Thanks, applied to ALSA tree now. Should be merged to 2.6.21. Takashi