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 X-Spam-Level: X-Spam-Status: No, score=-5.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AC4EC433E2 for ; Fri, 28 Aug 2020 07:27:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5C2D20CC7 for ; Fri, 28 Aug 2020 07:27:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598599670; bh=ZKgBgkPLZoJc/kStyrmzO8ZmcG3Mtvo7x+SL2dAs6h4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=SCvpRLXt+x7fmq9lBA3uH22hvFGxIhBeJKKYBGs/Bl9YdoVsRl+OJYkYpRc5asEeI FXtnW5pZLu1FL9LKI0VJgwYsEOlfrpXFN0FDy3E7G6ALNMD95mej0tkLdmfhc1wm16 Ij5X6R/w39tOaADQ4Jj5/9Icqfjc4Ezcd5vBNky8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728210AbgH1H1s (ORCPT ); Fri, 28 Aug 2020 03:27:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:35710 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726500AbgH1H1r (ORCPT ); Fri, 28 Aug 2020 03:27:47 -0400 Received: from localhost (unknown [122.171.38.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 3E4A1208CA; Fri, 28 Aug 2020 07:27:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1598599667; bh=ZKgBgkPLZoJc/kStyrmzO8ZmcG3Mtvo7x+SL2dAs6h4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=JAD8CL0Erh/teDxbTuuqQKHrcaC4IOjBehDT+dOCTzkSzWeRm6aLY/L0GxdYa0VnE umaTSwvQm7Jz3t9C7KjMKDt1NSAEiLqpHxe2pHdHW/GGem0ordiP4IKnZlBnVwoZOC G6rH4GRVGr2R2TSr3mFocrivVjQ7KYGo09mAQc94= Date: Fri, 28 Aug 2020 12:57:42 +0530 From: Vinod Koul To: Pierre-Louis Bossart Cc: Bard Liao , alsa-devel@alsa-project.org, tiwai@suse.de, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, ranjani.sridharan@linux.intel.com, hui.wang@canonical.com, broonie@kernel.org, srinivas.kandagatla@linaro.org, jank@cadence.com, mengdong.lin@intel.com, sanyog.r.kale@intel.com, rander.wang@linux.intel.com, bard.liao@intel.com Subject: Re: [PATCH 05/11] soundwire: bus: update multi-link definition with hw sync details Message-ID: <20200828072742.GL2639@vkoul-mobl> References: <20200818024120.20721-1-yung-chuan.liao@linux.intel.com> <20200818024120.20721-6-yung-chuan.liao@linux.intel.com> <20200826094420.GA2639@vkoul-mobl> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26-08-20, 09:09, Pierre-Louis Bossart wrote: > > > > > + * @hw_sync_min_links: Number of links used by a stream above which > > > + * hardware-based synchronization is required. This value is only > > > + * meaningful if multi_link is set. If set to 1, hardware-based > > > + * synchronization will be used even if a stream only uses a single > > > + * SoundWire segment. > > > > Soundwire spec does not say anything about multi-link so this is left to > > implementer. Assuming that value of 1 would mean hw based sync will > > be used even for single stream does not make sense in generic terms. > > Maybe yes for Intel but may not be true for everyone? > > hw-based sync is required for Intel even for single stream. It's been part > of the recommended programming flows since the beginning but ignored so far. > > That said, this value is set by each master implementation, no one forces > non-Intel users to implement an Intel-specific requirement. > > > We already use m_rt_count in code for this, so the question is why is > > that not sufficient? > > Because as you rightly said above, Intel requires the hw_sync to be used > even for single stream, but we didn't want others to be forced to use the > hw-sync for single stream. the m_rt_count is not sufficient for Intel. > > I think we are in agreement on not forcing everyone to follow what is > required by Intel, and that's precisely why we added this setting. If you > set it to two you would only use hw_sync when two masters are used. Okay, it would be better if we move it to intel driver, but I see it may not be trivial, so lets go with this approach. -- ~Vinod