From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f50.google.com ([209.85.214.50]:48969 "EHLO mail-bk0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753004Ab3HQM0p (ORCPT ); Sat, 17 Aug 2013 08:26:45 -0400 Received: by mail-bk0-f50.google.com with SMTP id mz11so959931bkb.9 for ; Sat, 17 Aug 2013 05:26:44 -0700 (PDT) From: Tomasz Figa Subject: Re: [PATCH v5 1/2] ASoC: fsl: Add S/PDIF CPU DAI driver Date: Sat, 17 Aug 2013 14:26:40 +0200 Message-ID: <137675716.iLf1T1CVZo@flatron> In-Reply-To: <20130816085632.GO26614@pengutronix.de> References: <20130816080124.GE1846@MrMyself> <20130816085632.GO26614@pengutronix.de> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: devicetree-owner@vger.kernel.org To: Sascha Hauer Cc: Nicolin Chen , ian.campbell@citrix.com, pawel.moll@arm.com, galak@codeaurora.org, broonie@kernel.org, lars@metafoo.de, p.zabel@pengutronix.de, linuxppc-dev@lists.ozlabs.org, alsa-devel@alsa-project.org, devicetree@vger.kernel.org, timur@tabi.org, rob.herring@calxeda.com, shawn.guo@linaro.org, festevam@gmail.com, swarren@wwwdotorg.org, mark.rutland@arm.com List-ID: On Friday 16 of August 2013 10:56:32 Sascha Hauer wrote: > On Fri, Aug 16, 2013 at 04:01:25PM +0800, Nicolin Chen wrote: > > Hi Sascha, > > > > Thank you for the detailed comments. > > > > On Fri, Aug 16, 2013 at 09:08:18AM +0200, Sascha Hauer wrote: > > > Which of them the driver should use is configuration and thus > > > normally > > > should *not* be described in the devicetree. However, there may be > > > no > > > good way for the driver to know which clock to use in which case. > > > There > > > may be additional board requirements which are unknown to the > > > driver. So in this case it might be valid to put the information > > > which clock to use into the devicetree. But be aware that from the > > > moment you put this information into the devicetree the driver is > > > no longer free to chose the best clock, even if in future we find a > > > good way to automatically guess the best clock. Do you have some > > > insights in which case I would use which input clock? Is this only > > > about which clock has the best suitable input frequency or is this > > > also about synchronization of the audio signal with some other > > > unit? > > > > I understand. What I'm thinking now is to let the driver find the best > > clock source for tx clock and a correspond divisor like this: > > > > "tx<0-8>" Optional Tx clock source for spdif playback. > > > > If absent, will use core clock. > > The index from 0 to 8 is identical > > to the clock source list described > > in TxClk_Source bit of register STC. > > Multiple clock source are allowed > > for this tx clock source. The driver > > will select one source from them for > > each supported sample rate according > > to the clock rates of these provided > > clock sources. > > You mean tx<0-7>. > > Also I would make this option required. Use a dummy clock for mux inputs > that are grounded for a specific SoC. Why do you need a dummy clock? The driver can simply try to grab all the possible clocks and discard those that failed, so you can just keep those grounded clocks unspecified. Best regards, Tomasz