From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-x244.google.com (mail-pg0-x244.google.com [IPv6:2607:f8b0:400e:c05::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3xsxwt5W8QzDrCn for ; Thu, 14 Sep 2017 09:01:18 +1000 (AEST) Received: by mail-pg0-x244.google.com with SMTP id m30so738332pgn.5 for ; Wed, 13 Sep 2017 16:01:18 -0700 (PDT) Date: Wed, 13 Sep 2017 16:01:48 -0700 From: Nicolin Chen To: Arnaud Mouiche Cc: broonie@kernel.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, alsa-devel@alsa-project.org, tiwai@suse.com, perex@perex.cz, lgirdwood@gmail.com, fabio.estevam@nxp.com, timur@tabi.org, lukma@denx.de, caleb@crome.org, max.krummenacher@toradex.com, mpa@pengutronix.de, mail@maciej.szmigiero.name Subject: Re: [PATCH] ASoC: fsl_ssi: Override bit clock rate based on slot number Message-ID: <20170913230147.GA21287@Asurada-Nvidia> References: <1504848223-3376-1-git-send-email-nicoleotsuka@gmail.com> <2020d72a-4517-55d0-59a1-171c71f91c7b@invoxia.com> <20170912213233.GA11419@Asurada-Nvidia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed, Sep 13, 2017 at 10:02:20AM +0200, Arnaud Mouiche wrote: > >Could you please give me a few set of examples of how you set > >set_sysclk(), set_tdm_slot() with the current driver? The idea > >here is to figure out a way to calculate the bclk in hw_params > >without getting set_sysclk() involved any more. > Here is one, where a bclk = 4*16*fs is expected > In another setup, there are 8 x 16 bits slots, whatever the number > of active channels is. > In this case bclk = 128 * fs > The number of slots is completely arbitrary. Some slots can even be > reserved for communication between codecs that don't communicate > with linux. In summary, bclk = sample rate * slots * slot_width; I will update my patch soon. > >Unfortunately, it looks like a work around to me. I understand > >the idea of leaving set_sysclk() out there to override the bit > >clock is convenient, but it is not a standard ALSA design and > >may eventually introduce new problems like today. > > I agree. I'm not conservative at all concerning this question. > I don't see a way to remove set_sysclk without breaking current TDM > users anyway, at least for those who don't have their code > upstreamed. Which TDM case would be broken by this removal? The only impact that I can see is that the ASoC core returns an ENOTSUPP for a set_sysclk() call now, which is something that a dai-link driver should have taken care of anyway. > All information provided through snd_soc_dai_set_tdm_slot( cpu_dai, > mask, mask, slots, width ) should be enough > In this case, for TDM users > > bclk = slots * width * fs (where slots is != channels) > will manage 99 % of the cases. > And the remaining 1% will concern people who need to hack the kernel > so widely they don't care about the set_sysclk removal. A patch from those people will be always welcome. > - fsl-asoc-card.c : *something will break since > snd_soc_dai_set_sysclk returned code is checked* I've already submitted a patch to ignore all ENOTSUPP.