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 966F6C38142 for ; Mon, 23 Jan 2023 15:50:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232923AbjAWPuV (ORCPT ); Mon, 23 Jan 2023 10:50:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55930 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232901AbjAWPuT (ORCPT ); Mon, 23 Jan 2023 10:50:19 -0500 Received: from mga18.intel.com (mga18.intel.com [134.134.136.126]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7A5F213D65 for ; Mon, 23 Jan 2023 07:50:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1674489017; x=1706025017; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=q/p7R22Dwd1VnE4UdAz1vguL9rsClepsQ5XC723K8bw=; b=TZwgMFvttfOgpKOFNvJecRMsFvH3WZkN6er8B967l6BRQ5HXGr32Wc3R Wz0aNFT+05kzRBqNZt/ac2QyX+KWF8KuxZTYUy2VBBSktdCaW0XF73ebz 8cB1nX1Eb4npYb2aEYYXtv6eF4/AGK0D27t8cqbRh4ysazu+ePea/wykJ sxOOTn6rwW5k5sDa4H/t/bQpBUe3zHpO08w7eqd1CTO/osLA/XTWTyovW pYeI+J773xa4Yvks+J3vZrPu/B/nQPMXsdh/ibwxEeLa3JcqiyZYqgegH QtaffJ9mzQOZV8RGe2NJW45OOj/i4ugUU6A4VPsQiGBbHwprhtq389gz8 A==; X-IronPort-AV: E=McAfee;i="6500,9779,10599"; a="309647185" X-IronPort-AV: E=Sophos;i="5.97,240,1669104000"; d="scan'208";a="309647185" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2023 07:50:17 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10599"; a="693952499" X-IronPort-AV: E=Sophos;i="5.97,240,1669104000"; d="scan'208";a="693952499" Received: from rgrachek-mobl.amr.corp.intel.com (HELO [10.212.113.123]) ([10.212.113.123]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 23 Jan 2023 07:50:16 -0800 Message-ID: <034245f8-50b7-e801-7961-58c77dbc00b1@linux.intel.com> Date: Mon, 23 Jan 2023 09:50:15 -0600 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.4.2 Subject: Re: [PATCH 2/2] soundwire: bus: Allow SoundWire peripherals to register IRQ handlers Content-Language: en-US To: Charles Keepax Cc: alsa-devel@alsa-project.org, patches@opensource.cirrus.com, linux-kernel@vger.kernel.org, vkoul@kernel.org, sanyog.r.kale@intel.com, yung-chuan.liao@linux.intel.com References: <20230119165104.3433290-1-ckeepax@opensource.cirrus.com> <20230119165104.3433290-2-ckeepax@opensource.cirrus.com> <20230120095941.GL36097@ediswmail.ad.cirrus.com> <881088ad-95d7-2462-20d2-72a6a9d3ba68@linux.intel.com> <20230123145353.GX36097@ediswmail.ad.cirrus.com> From: Pierre-Louis Bossart In-Reply-To: <20230123145353.GX36097@ediswmail.ad.cirrus.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/23/23 08:53, Charles Keepax wrote: > On Fri, Jan 20, 2023 at 10:20:50AM -0600, Pierre-Louis Bossart wrote: >> On 1/20/23 03:59, Charles Keepax wrote: >>> On Thu, Jan 19, 2023 at 11:12:04AM -0600, Pierre-Louis Bossart wrote: >>>> There should be an explanation and something checking that both are not >>>> used concurrently. >>> >>> I will try to expand the explanation a litte, but I dont see any >>> reason to block calling both handlers, no ill effects would come >>> for a driver having both and it is useful if any soundwire >>> specific steps are needed that arn't on other control buses. >> >> I think it's problematic if the peripheral tries to wake-up the manager >> from clock-stop with both an in-band wake (i.e. drive the data line >> high) and a separate GPIO-based interrupt. It's asking for trouble IMHO. >> We spent hours in the MIPI team to make sure there were no races between >> the manager-initiated restarts and peripheral-initiated restarts, adding >> a 3rd mechanism in the mix gives me a migraine already. > > Apologies but I am struggling see why this has any bearing on > the case of a device that does both an in-band and out-of-band > wake. The code we are adding in this patch will only be called in the > in-band case. handle_nested_irq doesn't do any hardware magic or > schedule any threads, it just calls a function that was provided > when the client called request_threaded_irq. The only guarantee > of atomicity you have on the interrupt_callback is sdw_dev_lock > and that is being held across both calls after the patch. > > Could you be a little more specific on what you mean by this > represents a 3rd mechanism, to me this isn't a new mechanism just > an extra callback? Say for example this patch added an > interrupt_callback_early to sdw_slave_ops that is called just > before interrupt_callback. Well, the main concern is exiting the clock-stop. That is handled by the manager and could be done a) as the result of the framework deciding that something needs to be done (typically as a result of user/applications starting a stream) b) by the device with an in-band wake in case of e.g. jack detection or acoustic events detected c) same as b) but with a separate out-of-band interrupt. I'd like to make sure b) and c) are mutually-exclusive options, and that the device will not throw BOTH an in-band wake and an external interrupt.