Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755023AbaBDS7U (ORCPT ); Tue, 4 Feb 2014 13:59:20 -0500 Received: from smtpfb1-g21.free.fr ([212.27.42.9]:40548 "EHLO smtpfb1-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751357AbaBDS7R convert rfc822-to-8bit (ORCPT ); Tue, 4 Feb 2014 13:59:17 -0500 Date: Tue, 4 Feb 2014 19:59:21 +0100 From: Jean-Francois Moine To: Mark Brown Cc: alsa-devel@alsa-project.org, Dave Airlie , dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Rob Clark , Russell King - ARM Linux Subject: Re: [PATCH v3 2/5] ASoC: tda998x: add a codec driver for the TDA998x Message-ID: <20140204195921.5ace6163@armhf> In-Reply-To: <20140204175410.GL22609@sirena.org.uk> References: <20140204133014.GA22609@sirena.org.uk> <20140204181605.5b837a70@armhf> <20140204175410.GL22609@sirena.org.uk> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 4 Feb 2014 17:54:10 +0000 Mark Brown wrote: > On Tue, Feb 04, 2014 at 06:16:05PM +0100, Jean-Francois Moine wrote: > > Mark Brown wrote: > > > > > + /* load the optional CODEC */ > > > > + of_platform_populate(np, NULL, NULL, &client->dev); > > > > Why is this using of_platform_populate()? That's a very odd way of > > > doing things. > > > The i2c does not populate the subnodes in the DT. I did not find why, > > but, what is sure is that if of_platform_populate() is not called, the > > tda CODEC module is not loaded. > > You shouldn't be representing this as a separate node in the DT unless > there really is a distinct and reusable IP, otherwise you're putting > Linux implementation details in there. Describe the hardware, not the > implemementation. If there is no 'compatible' node for the tda998x CODEC in the DT, the simple-card is not usable, simply because you want the CODEC DAIs to be defined by 'phandle + index' instead of by DAI name. > > You may find an other example in drivers/mfd/twl-core.c. > > The TWL drivers aren't always a shining example of how to do things - > they were one of the earliest MFDs so there's warts in there. > > > > > +config SND_SOC_TDA998X > > > > + tristate > > > > + depends on OF > > > > + default y if DRM_I2C_NXP_TDA998X=y > > > > + default m if DRM_I2C_NXP_TDA998X=m > > > > Make this visible if it can be selected from DT so it can be used with > > > generic cards. > > > I don't understand. The tda CODEC can only be used with the TDA998x I2C > > driver. It might have been included in the tda998x source as well. > > You shouldn't have the default settings there at all, that's not the > normal idiom for MFDs. I'd also not expect to have to build the CODEC > driver just because I built the DRM component. As the tda998x handles audio in HDMI, it would be a pity if you should connect an other cable to your screen. > > Now, the CODEC is declared inside the tda998x as a node child. But, in > > a bad DT, the tda CODEC could be declared anywhere, even inside a other > > DRM I2C slave encoder, in which case, bad things would happen... > > So, part of the problem here is that this is being explicitly declared > in the DT leading to more sources for error. Simple-card constraint. > > > What does this actually do? No information is being passed in to the > > > core function here, not even any information on if it's starting or > > > stopping. Looking at the rest of the code I can't help thinking it > > > might be clearer to inline this possibly with a lookup helper, the code > > > is very small and the lack of parameters makes it hard to follow. > > > I thought it was simple enough. The function tda_start_stop() is called > > from 2 places: > > It's not at all obvious - _audio_update() isn't a terribly descriptive > name, just looking at that function by itself I had no idea what it was > supposed to be doing. The first purpose of the function is to set the audio input port in the tda998x. Streaming stop could have been omitted, but I thought it could be interesting to stop HDMI audio when there is a super HiFi device connected to the S/PDIF connector. > > - on audio start in tda_startup with the audio type (DAI id) > > priv->dai_id = dai->id; > > > - on audio stop with a null audio type > > priv->dai_id = 0; /* streaming stop */ > > > On stream start, the DAI id is never null, as explained in the patch 1: > > > The audio format values in the encoder configuration interface are > > changed to non null values so that the value 0 is used in the audio > > function to indicate that audio streaming is stopped. > > > and on streaming stop the port is not meaningful. > > > I will add a null item in the enum (AFMT_NO_AUDIO). > > So we can't use both streams simultaneously then? That's a bit sad. That's how the NXP tda998x family works (and surely many other HDMI transmitters). So, as I understand from your remarks, the CODEC should be included in the tda998x driver, and, then, as the simple-card cannot be used, there should be a Cubox specific audio card driver for the (kirkwood audio + tda998x HDMI + S/PDIF) set. Am I right? -- Ken ar c'hentañ | ** Breizh ha Linux atav! ** Jef | http://moinejf.free.fr/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/