From mboxrd@z Thu Jan 1 00:00:00 1970 From: Liam Girdwood Subject: Re: [PATCH 2/2] ASoC: omap: Stop DMA re enabling in self linkage mode Date: Tue, 07 Dec 2010 15:17:34 +0000 Message-ID: <1291735054.3275.86.camel@odin> References: <1889FA7136B567478A67D4B0F85B0CCEA4C52E81@dlee06.ent.ti.com> <201012071117.26440.peter.ujfalusi@nokia.com> <20101207140512.GX4698@rakim.wolfsonmicro.main> <201012071638.36075.peter.ujfalusi@nokia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ww0-f51.google.com (mail-ww0-f51.google.com [74.125.82.51]) by alsa0.perex.cz (Postfix) with ESMTP id BD9AD2414E for ; Tue, 7 Dec 2010 16:17:37 +0100 (CET) Received: by wwe15 with SMTP id 15so6810wwe.20 for ; Tue, 07 Dec 2010 07:17:37 -0800 (PST) In-Reply-To: <201012071638.36075.peter.ujfalusi@nokia.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: Peter Ujfalusi Cc: "ext Olaya, Margarita" , alsa-devel@alsa-project.org, ext Mark Brown List-Id: alsa-devel@alsa-project.org On Tue, 2010-12-07 at 16:38 +0200, Peter Ujfalusi wrote: > On Tuesday 07 December 2010 16:05:12 ext Mark Brown wrote: > > On Tue, Dec 07, 2010 at 11:17:26AM +0200, Peter Ujfalusi wrote: > > > I have not seen this happening on OMAP2/3, or at least I'm not aware of > > > it. Is this problem OMAP4 only? > > > Do you know if this happens on playback, capture or in both direction? > > > Is it worth to do this workaround only on OMAP4? > > > > Given that the patch should cause at most a single read from a register > > when tearing down DMA if it's not required I'd guess it's safer to just > > unconditionally enable the workaround on the off chance that it's just > > reallly rare rather than not needed? > > Sure, it is a single read to a register, but generally I'm a bit nervous, when > we have a while loop without timeout counter. > In theory we could have infinite loop, if the HW has a bad day... > This could be safe on all OMAP platforms, but I think it has been only tested on > OMAP4. > If this could happen, than IMHO it has to be handled by the omap_stop_dma, since > other drivers could be hit by the same problem (there might be ERRATA for it > already for OMAP4). > Afaik, this has also been tested on OMAP3. Not sure about OMAP2 and most likely not tested on OMAP1. Liam