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 181C7C05027 for ; Mon, 23 Jan 2023 17:18:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233554AbjAWRS1 (ORCPT ); Mon, 23 Jan 2023 12:18:27 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55082 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233513AbjAWRSZ (ORCPT ); Mon, 23 Jan 2023 12:18:25 -0500 Received: from mx0b-001ae601.pphosted.com (mx0a-001ae601.pphosted.com [67.231.149.25]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD00B2331C for ; Mon, 23 Jan 2023 09:18:04 -0800 (PST) Received: from pps.filterd (m0077473.ppops.net [127.0.0.1]) by mx0a-001ae601.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 30NCQVVr019412; Mon, 23 Jan 2023 11:17:55 -0600 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cirrus.com; h=message-id : date : mime-version : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding; s=PODMain02222019; bh=ikFhvFMwhwbSTa3ZoN4u9/ntqlbcXVmKikN+51+w++s=; b=JdqJUiOKTJWNyc6UUQWImMObDlEGWdtGns40B2VmLyH8uQPPTUyyALf84z0yTwvVwmYI TSHNMNDhJrf8xcAUE6BC0wQNzCXnYoVA8QvDjt7jQR++hJKMMg9db4t/y6NIMAid+njA 6Avy4VN9agusdEF1dwQr4mahsQKRbLoo+S3XCI9BDfBHMlq5wlKoMmN/dBIojLjLLmha YbDZJPg7VcXVPg87c+hjiphYing+9xhGMpPw4YH79fF2t/KJxZIrae0PDfpA5T1ZbjDq 1tdXSmXRZ9rYdf8cmIn6Q30MA+zlpCJNXjVdZmbXpHmHidb3oOoUMfCC9cqDUeFkjsjG 1A== Received: from ediex01.ad.cirrus.com ([84.19.233.68]) by mx0a-001ae601.pphosted.com (PPS) with ESMTPS id 3n8eb5ud9r-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 23 Jan 2023 11:17:55 -0600 Received: from ediex02.ad.cirrus.com (198.61.84.81) by ediex01.ad.cirrus.com (198.61.84.80) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1118.21; Mon, 23 Jan 2023 11:17:52 -0600 Received: from ediswmail.ad.cirrus.com (198.61.86.93) by anon-ediex02.ad.cirrus.com (198.61.84.81) with Microsoft SMTP Server id 15.2.1118.7 via Frontend Transport; Mon, 23 Jan 2023 11:17:52 -0600 Received: from [198.90.251.127] (edi-sw-dsktp-006.ad.cirrus.com [198.90.251.127]) by ediswmail.ad.cirrus.com (Postfix) with ESMTP id EC93FB06; Mon, 23 Jan 2023 17:17:52 +0000 (UTC) Message-ID: <8a05bb50-9743-d3cc-cff7-8b93aa1f68df@opensource.cirrus.com> Date: Mon, 23 Jan 2023 17:17:52 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH 2/2] soundwire: bus: Allow SoundWire peripherals to register IRQ handlers Content-Language: en-US To: Pierre-Louis Bossart , Charles Keepax CC: , , , , , 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> <034245f8-50b7-e801-7961-58c77dbc00b1@linux.intel.com> <05a00da2-2ff8-b234-3959-b451849b8cdb@opensource.cirrus.com> <638af695-3874-7c1f-830a-09cf353f45fb@linux.intel.com> From: Richard Fitzgerald In-Reply-To: <638af695-3874-7c1f-830a-09cf353f45fb@linux.intel.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-GUID: PMVdj0bbhGczgy6a1MICN2d_HlrQs0Jr X-Proofpoint-ORIG-GUID: PMVdj0bbhGczgy6a1MICN2d_HlrQs0Jr X-Proofpoint-Spam-Reason: safe Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 23/01/2023 16:38, Pierre-Louis Bossart wrote: > > > On 1/23/23 10:08, Richard Fitzgerald wrote: >> On 23/01/2023 15:50, Pierre-Louis Bossart wrote: >>> >>> >>> 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. >> >> Why would it be a problem if the device did (b) and (c)? >> (c) is completely invisible to the SoundWire core and not something >> that it has to handle. The handler for an out-of-band interrupt must >> call pm_runtime_get_sync() or pm_runtime_resume_and_get() and that >> would wake its own driver and the host controller. > > The Intel hardware has a power optimization for the clock-stop, which > leads to different paths to wake the system. The SoundWire IP can deal > with the data line staying high, but in the optimized mode the wakes are > signaled as DSP interrupts at a higher level. That's why we added this > intel_link_process_wakeen_event() function called from > hda_dsp_interrupt_thread(). > > So yes on paper everything would work nicely, but that's asking for > trouble with races left and right. In other words, unless you have a Wake up from a hard INT is simply a runtime_resume of the codec driver. That is no different from ASoC runtime resuming the driver to perform some audio activity, or to access a volatile register. An event caused a runtime-resume - the driver and the host controller must resume. The Intel code _must_ be able to safely wakeup from clock-stop if something runtime-resumes the codec driver. ASoC relies on that, and pm_runtime would be broken if that doesn't work. > very good reason for using two wake-up mechanisms, pick a single one. > > (a) and (c) are very similar in that all the exit is handled by > pm_runtime so I am not worried too much. I do worry about paths that > were never tested and never planned for.