From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757639AbbAIN7D (ORCPT ); Fri, 9 Jan 2015 08:59:03 -0500 Received: from fw-tnat.cambridge.arm.com ([217.140.96.140]:39876 "EHLO cam-smtp0.cambridge.arm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754843AbbAIN7B (ORCPT ); Fri, 9 Jan 2015 08:59:01 -0500 Message-ID: <54AFDE8D.3000504@arm.com> Date: Fri, 09 Jan 2015 13:58:37 +0000 From: Andrew Jackson User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.3.0 MIME-Version: 1.0 To: Russell King - ARM Linux , Jean-Francois Moine CC: Jyri Sarha , Mark Brown , Dave Airlie , "alsa-devel@alsa-project.org" , "devicetree@vger.kernel.org" , "dri-devel@lists.freedesktop.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v9 1/4] drm/i2c: tda998x: Add DT support for audio References: <0084acea5a3475a77531d6a77483f36d3469111a.1420628786.git.moinejf@free.fr> <54AE99F5.1010404@ti.com> <20150108174257.557f7ea5@armhf> <54AFA9B0.6040405@ti.com> <20150109123036.4bc4bbf6@armhf> <20150109114529.GH12302@n2100.arm.linux.org.uk> <20150109135401.5b270d46@armhf> <20150109130725.GN12302@n2100.arm.linux.org.uk> In-Reply-To: <20150109130725.GN12302@n2100.arm.linux.org.uk> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/09/15 13:07, Russell King - ARM Linux wrote: > On Fri, Jan 09, 2015 at 01:54:01PM +0100, Jean-Francois Moine wrote: >> On Fri, 9 Jan 2015 11:45:29 +0000 >> Russell King - ARM Linux wrote: >>> I think we need to understand exactly how the 998x map I2S inputs to the >>> HDMI channels to avoid making a mistake with the binding; remember, the >>> binding isn't something that can be easily "bug fixed" at a later date >>> as anything we come up with now has to be supported long term by the >>> kernel. >> >> The DT describes the hardware configuration. > > You're missing my point. > > How does the driver know which of the I2S pins to enable in I2S mode? [snip] > My question is: how do we know which I2S inputs to enable, or are > you suggesting that all I2S inputs should be enabled if operating in > I2S mode irrespective of whether they may be active? > Isn't it the case that for I2S: * Word Select (WS) is always required to disambiguate left/right. So WS need not be specified in any device tree configuration. * The audio inputs depend on a particular board but at least one is required. Fortunately, the TDA998x devices have all the same pin/input numbering so they /could/ be described as i2s0, i2s1, i2s2 and i2s3 as per J-F's earlier email. But tt isn't clear from my reading of the TDA19988 datasheet (for example) whether one can skip channels (so does channel 0 always have to be present?). If the channels must be enabled from 0 then one could simply specify the number of inputs. (The datasheets that I have don't indicate whether there's any channel remapping performed internally by the TDA998x). * What the driver does need to take account of is the number of inputs that are active so that the sound CODEC can be properly configured. Andrew