From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Brown Subject: Re: [PATCH 1/2] powerpc: add platform registration for ALSA SoC drivers Date: Tue, 27 Apr 2010 22:11:18 +0100 Message-ID: <20100427211118.GD15083@opensource.wolfsonmicro.com> References: <1272314980-23679-1-git-send-email-timur@freescale.com> <1272350168.24542.6.camel@pasglop> <1272355624.3204.52.camel@odin> <4BD74D0C.40303@freescale.com> <20100427205924.GC15083@opensource.wolfsonmicro.com> <4BD7511F.7090201@freescale.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from opensource2.wolfsonmicro.com (opensource.wolfsonmicro.com [80.75.67.52]) by alsa0.perex.cz (Postfix) with ESMTP id 3EB0C24371 for ; Tue, 27 Apr 2010 23:11:19 +0200 (CEST) Content-Disposition: inline In-Reply-To: <4BD7511F.7090201@freescale.com> 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: Timur Tabi Cc: alsa-devel@alsa-project.org, Benjamin Herrenschmidt , kumar.gala@freescale.com, Grant Likely , linuxppc-dev@ozlabs.org, Liam Girdwood List-Id: alsa-devel@alsa-project.org On Tue, Apr 27, 2010 at 04:03:27PM -0500, Timur Tabi wrote: [Reflowing the text into 80 columns again] > Mark Brown wrote: > > It's entirely possible that if the board designer intended the verious > > SSIs to be used in concert they've done something like cross wire the > > clocks which creates a board-specific interrelationship that needs to be > > dealt with. > Fine, but I don't see how that can be handled with the current code. > Each SSI is independent, and audio is streamed to it via DMA. The > current SSI driver would need to be completely rewritten in order to > initiate both DMA operations simultaneously. The clocking is the least > of my problems. I believe the usual technique is to start the DMA then clock the bus - data doesn't flow over the bus until the clock appears and that appears everywhere simultaneously. Obviously some hardware really doesn't like having the DMA blocked like that, but not all.