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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 573F0C433E0 for ; Tue, 2 Mar 2021 19:47:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1520D64F07 for ; Tue, 2 Mar 2021 19:47:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1577098AbhCBSbP (ORCPT ); Tue, 2 Mar 2021 13:31:15 -0500 Received: from mx1.opensynergy.com ([217.66.60.4]:46959 "EHLO mx1.opensynergy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1578956AbhCBPgO (ORCPT ); Tue, 2 Mar 2021 10:36:14 -0500 Received: from SR-MAILGATE-02.opensynergy.com (localhost.localdomain [127.0.0.1]) by mx1.opensynergy.com (Proxmox) with ESMTP id CE368A178A; Tue, 2 Mar 2021 16:35:25 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=opensynergy.com; h=cc:cc:content-transfer-encoding:content-type:content-type :date:from:from:in-reply-to:message-id:mime-version:references :reply-to:subject:subject:to:to; s=srmailgate02; bh=3sXhMOkM8LPe kLQJ3JvWQSiaoISGZyoWfcdIHtOJozw=; b=mzldlBoLn0NX3gqduhq7oHrlZOp4 MdnN2j6nmr6SccEt9rMCwx1Fp9sfgTRp2Xe6VfqzGoIFItrsWos7VfFvvhtvRi1z ZVD61qHZQN2ajz0hY0ktQzvf7Xa3HhObJtZJObTvK7V7LmxRu3zsorJh7ssWYK9m D8LrFdlko5HsOJR1tUimCA5eViDiEAc/vnKXjvkd5aGqlN26tU8eZSeoydpk9qm0 RMr2dArQLodtJXuUw6Rm6gzeWAmMgNIy/wWdroW2gMDrbADAO9PQLDkohZAvpDSl rZrbXOSx2dpsYLzYPYiaUBSzyz/N+4tphZJkTS6d1NBaW4yeCiR78tCmuA== Subject: Re: [PATCH v6 9/9] ALSA: virtio: introduce device suspend/resume support To: Takashi Iwai CC: , , , "Michael S. Tsirkin" , Jaroslav Kysela , Takashi Iwai , References: <20210227085956.1700687-1-anton.yakovlev@opensynergy.com> <20210227085956.1700687-10-anton.yakovlev@opensynergy.com> <7d4daea0-ed59-e84c-c28a-945c49204c83@opensynergy.com> From: Anton Yakovlev Message-ID: <2479ed0f-4c90-f565-81cd-8d0348cd14bc@opensynergy.com> Date: Tue, 2 Mar 2021 16:35:24 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-ClientProxiedBy: SR-MAIL-01.open-synergy.com (10.26.10.21) To SR-MAIL-01.open-synergy.com (10.26.10.21) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02.03.2021 10:11, Takashi Iwai wrote: > On Tue, 02 Mar 2021 09:09:33 +0100, > Anton Yakovlev wrote: >> >> On 02.03.2021 07:48, Takashi Iwai wrote: >>> On Tue, 02 Mar 2021 07:29:20 +0100, >>> Anton Yakovlev wrote: >>>> >>>> On 28.02.2021 13:05, Takashi Iwai wrote: >>>>> On Sat, 27 Feb 2021 09:59:56 +0100, >>>>> Anton Yakovlev wrote: >>>>>> >>>> >>>> [snip] >>>> >>>>>> --- a/sound/virtio/virtio_pcm.c >>>>>> +++ b/sound/virtio/virtio_pcm.c >>>>>> @@ -109,6 +109,7 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, >>>>>> SNDRV_PCM_INFO_BATCH | >>>>>> SNDRV_PCM_INFO_BLOCK_TRANSFER | >>>>>> SNDRV_PCM_INFO_INTERLEAVED | >>>>>> + SNDRV_PCM_INFO_RESUME | >>>>>> SNDRV_PCM_INFO_PAUSE; >>>>> >>>>> Actually you don't need to set SNDRV_PCM_INFO_RESUME. >>>>> This flag means that the driver supports the full resume procedure, >>>>> which isn't often the case; with this, the driver is supposed to >>>>> resume the stream exactly from the suspended position. >>>>> >>>>> Most drivers don't set this but implement only the suspend-stop >>>>> action. Then the application (or the sound backend) will re-setup the >>>>> stream and restart accordingly. >>>> >>>> I tried to resume driver without SNDRV_PCM_INFO_RESUME, and alsa-lib >>>> called only ops->prepare(). It makes sense for a typical hw, but we have >>>> "clean" unconfigured device on resume. And we must set hw parameters as >>>> a first step. It means, that code should be more or less the same. And >>>> maybe it's better to set SNDRV_PCM_INFO_RESUME, since it allows us to >>>> resume substream in any situation (regardless of application behavior). >>>> I can refactor code to only send requests from trigger(RESUME) path and >>>> not to call ops itself. It should make code more straitforward. What do >>>> you say? >>> >>> How about calling hw_params(NULL) conditionally in the prepare? >> >> Then the question is that condition. When ops->prepare() is called, the >> substream is in SUSPENDED state or not? If not then we need to track >> this in some additional field (and it will make logic a little bit >> clumsy, since that field is needed to be carefully handled in other >> places). > > Yes, you'd need to have a suspend/resume PM callback in the driver > that flips the internal flag to invalidate the hw_parmas, and in the > prepare callback, just call hw_params(NULL) if that flag is set. > >>> Doing the full stack work in the trigger callback is bad from the API >>> design POV; in general the trigger callback is supposed to be as short >>> as possible. >> >> Yeah, but usually original subsystem design does not take into account >> para-virtualized devices, which usually have it's own slightly different >> reality. And we need to introduce some tricks. > > The hardware drivers do a lot of more things in either suspend/resume > PM callbacks or prepare callback for re-setup of the hardware. We can > follow the similar pattern. Heavy-lifting works in the trigger > callbacks is really something to avoid. Ok, I redone this part and now the driver sets parameters for the device in ops->prepare() if the substream was suspended. And everything works fine. Thanks! I will send a new patch set soon. > Takashi > -- Anton Yakovlev Senior Software Engineer OpenSynergy GmbH Rotherstr. 20, 10245 Berlin