From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9C9A5C433F5 for ; Mon, 10 Jan 2022 16:49:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237761AbiAJQtZ (ORCPT ); Mon, 10 Jan 2022 11:49:25 -0500 Received: from mga03.intel.com ([134.134.136.65]:50943 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237732AbiAJQtY (ORCPT ); Mon, 10 Jan 2022 11:49:24 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1641833364; x=1673369364; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=RD9okIjLSTH7xkAaitQ8zmG3R2QSjQPLZHJurvli5Ng=; b=TGRQGLeQO9nWr4vrwHBz+78BtY7l7pKdABjcRL2GCwpyjHgQr1QHW+uf fF15I9n9l2HL8SR6LZw6df19B8+YqVqDQPMqOWd8Kx2hYZs0rXA7zZJoz otzCYNg65i16TXpdpSKlWzEsZtY/Tybvvog3XsHCYECo/QEK9Uh/S9C1g 161SStBN12eNGQBBdmXsFjKswFl6KqKnv2YdoPqno+dcRr2z+/Z1c5l+n +ffXlkPP4kubd3cnQqFHpaulm1ZG+FtKLaTmFcZOFoKU8IkTlTnejMVHU 1MVh2Av7byisK8dfO0H2bNV7zPB9yTotAz4PNw4EgvQ2tXUfh6HkKkpSK w==; X-IronPort-AV: E=McAfee;i="6200,9189,10222"; a="243219152" X-IronPort-AV: E=Sophos;i="5.88,277,1635231600"; d="scan'208";a="243219152" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jan 2022 08:49:11 -0800 X-IronPort-AV: E=Sophos;i="5.88,277,1635231600"; d="scan'208";a="472123479" Received: from boviedox-mobl.amr.corp.intel.com (HELO [10.212.36.191]) ([10.212.36.191]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 10 Jan 2022 08:49:11 -0800 Subject: Re: [PATCH 7/7] soundwire: intel: remove PDM support To: "Liao, Bard" , Vinod Koul Cc: "alsa-devel@alsa-project.org" , "tiwai@suse.de" , "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" , "broonie@kernel.org" , "srinivas.kandagatla@linaro.org" , "Kale, Sanyog R" , Bard Liao References: <20211213054634.30088-1-yung-chuan.liao@linux.intel.com> <20211213054634.30088-8-yung-chuan.liao@linux.intel.com> From: Pierre-Louis Bossart Message-ID: <0cb18de1-dcff-e3c8-414e-b5b96b30b387@linux.intel.com> Date: Mon, 10 Jan 2022 10:32:32 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>>>> While the hardware supports PDM streams, this capability has never >>>>> been tested or enabled on any product, so this is dead-code. Let's >>>>> remove all this. >>>> >>>> So no plans to test and enable this? Do the DMICs not use PDM? >>> >>> The point is that this code is unused/untested. We can re-add it after >>> it was tested. >> >> That does not answer my question. Do the DMICs not use PDM? > > I will leave the question to Pierre. 😊 traditional digital microphones using the Nokia spec with two microphones using opposite clock edges do use PDM. PDM over SoundWire is possible as well, it's e.g. used by Qualcomm for amplifiers. This patch does not make a statement on whether PDM support makes sense or not in general. As mentioned above on Intel platforms the hardware is in theory capable of supporting PDM, but that capability has never been deployed, all existing devices we connect to are PCM based and all the PDM references are essentially untested - and likely broken.