From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752462AbdIFRlF (ORCPT ); Wed, 6 Sep 2017 13:41:05 -0400 Received: from mail-pg0-f51.google.com ([74.125.83.51]:33627 "EHLO mail-pg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751328AbdIFRlD (ORCPT ); Wed, 6 Sep 2017 13:41:03 -0400 X-Google-Smtp-Source: ADKCNb4X7Z02JDSP19DU/3bdgoUS2PXe60awLk9phl5CVU5VnyhYhQBSvSCJvQY2KJYvxFHeAv8dqQ== Date: Wed, 6 Sep 2017 10:33:50 -0700 From: Nicolin Chen To: =?utf-8?Q?=C5=81ukasz?= Majewski Cc: Fabio Estevam , Timur Tabi , Xiubo Li , Liam Girdwood , Mark Brown , Jaroslav Kysela , Takashi Iwai , "festevam@gmail.com" , "alsa-devel@alsa-project.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] sound: soc: fsl: Do not set DAI sysclk when it is equal to system freq Message-ID: <20170906173348.GA28104@Asurada-Nvidia> References: <1504436701-20700-1-git-send-email-lukma@denx.de> <07e54d28-3bbc-aad2-146b-30867c0bc337@denx.de> <20170905052031.GB2774@Asurada-CZ80> <819784e1-910b-6833-997a-2097e147bd0c@denx.de> <20170905181108.GB23906@Asurada-Nvidia> <20170905225225.GA14132@Asurada-Nvidia> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 06, 2017 at 11:22:48AM +0200, Łukasz Majewski wrote: > >Here is the routine that I understood from the code: > >1) asoc_simple_card_parse_clk_cpu(dev, cpu, dai_link, cpu_dai); > > => asoc_simple_card_parse_clk(dev, cpu, // cpu node in sound{} [1] > > dai_link->cpu_of_node, // node ssi2 [2] > > cpu_dai, dai_link->cpu_dai_name); > > ==> 1.1) devm_get_clk_from_child(dev, node, NULL); // [1] > > ==> 1.2) of_property_read_u32(node, "system-clock-frequency", &val)// [1] > > ==> 1.3) devm_get_clk_from_child(dev, dai_of_node, NULL); // [2] > >For the cpu routine, it first checks for clock property under cpu > >node of simple-card, then for "system-clock-frequency" in the cpu > >node of simple-card, and finally looks for clock property in ssi2 > >node. > -----> dev: sound > -----> clk node: /soc/aips-bus@02000000/spba-bus@02000000/ssi@0202c000 > -----> Clk asignment > > And this clock is taken from this node. It looks like ipg clock for ssi... This makes sense now. The devm_get_clk_from_child() in 1.3) fetched the first clock of ssi2 -- ipg clock. > The problem is with the "lack" of clock nodes/properties at > > dailink_master: cpu { > sound-dai = <&ssi2>; > clock = <&SSSS>; > system-clock-frequency = ; > }; This is the right solution based on current simple-card driver. For SSI (having two clocks), you have to specify the baud clock in the cpu node like that. I believe this is what the simple-card designer expected users to do since the cpu node is the first place that the driver tries to look at. > I think that the proper solution would be to add check for: > > freq < sysclk/5 in fsl_ssi_set_dai_sysclk() and return -ENOTSUPP to > make the simple-audo-card driver happy (and not introducing > regressions). As I said in the first place, adding another check in set_sysclk() is not that essential but seems to be plausible to me. So I am okay if you really want to have that.