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=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 0F29CC433E0 for ; Wed, 20 May 2020 19:44:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DAEAF207ED for ; Wed, 20 May 2020 19:44:35 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="eyYjLL4b" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726827AbgETTof (ORCPT ); Wed, 20 May 2020 15:44:35 -0400 Received: from mail26.static.mailgun.info ([104.130.122.26]:21786 "EHLO mail26.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726548AbgETToe (ORCPT ); Wed, 20 May 2020 15:44:34 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1590003873; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=CAOGbNRPH8PavTHVA+eqY2zfyumPm9H6vlGj6V/xRYU=; b=eyYjLL4b9vohU6s6iNGgzdjj8VRWLaPh/ZqqDtFK16cVkj0Dr4oUOWbUwuQ1e3uuNaCFwRHg rA5KlrQ+8xgnJ/fhbDuux8oORsp2VU5o+wvYggAsPEzwqqxT6T9tXwbmeMYvpeM0SY+W26+C IXouT0s3HOZ87Snwv7R8CVGqf90= X-Mailgun-Sending-Ip: 104.130.122.26 X-Mailgun-Sid: WyI1MzIzYiIsICJsaW51eC1hcm0tbXNtQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n02.prod.us-east-1.postgun.com with SMTP id 5ec5889245598550e6976569 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Wed, 20 May 2020 19:44:18 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id D3A5DC433CB; Wed, 20 May 2020 19:44:17 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: bbhatt) by smtp.codeaurora.org (Postfix) with ESMTPSA id 9DADFC433C9; Wed, 20 May 2020 19:44:16 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Wed, 20 May 2020 12:44:16 -0700 From: bbhatt@codeaurora.org To: Jeffrey Hugo Cc: manivannan.sadhasivam@linaro.org, linux-arm-msm@vger.kernel.org, hemantk@codeaurora.org, linux-kernel@vger.kernel.org, linux-kernel-owner@vger.kernel.org Subject: Re: [PATCH v3 2/7] bus: mhi: core: Introduce independent voting mechanism In-Reply-To: References: <1589832241-13867-1-git-send-email-bbhatt@codeaurora.org> <1589832241-13867-3-git-send-email-bbhatt@codeaurora.org> <574a4fe915f86608b59f10577eb960e9@codeaurora.org> Message-ID: <70f32d3dfc9dd81163897a57ebe35d02@codeaurora.org> X-Sender: bbhatt@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On 2020-05-20 12:06, Jeffrey Hugo wrote: > On 5/20/2020 12:43 PM, bbhatt@codeaurora.org wrote: >> On 2020-05-20 09:54, Jeffrey Hugo wrote: >>> On 5/18/2020 2:03 PM, Bhaumik Bhatt wrote: >>>> Allow independent votes from clients such that they can choose to >>>> vote >>>> for either the device or the bus or both. This helps in cases where >>>> the >>>> device supports autonomous low power mode wherein it can move to M2 >>>> state without the need to notify the host. Clients can also vote >>>> only to >>>> keep the underlying bus active without having the device in M0 state >>>> to >>>> support offload use cases. >>>> >>>> Signed-off-by: Bhaumik Bhatt >>>> --- >>> >>> I wonder, why doesn't this fit with runtimePM? >> Hi Jeff, >> >> Can you elaborate? >> >> In short, with this patch, MHI just wants to give controller the >> option to >> choose the vote type so we can implement autonomous low power mode >> entries >> on both host and device. > > So, you are attempting to manage the power mode of the device. The > standard mechanism to do so in Linux is runtime pm. > > https://elixir.bootlin.com/linux/latest/source/Documentation/driver-api/pm/devices.rst > > I'm no runtime pm expert, but it feels like your whole voting > mechanism, etc is just reimplemeting that. Reimplementing the wheel, > when its been a standard thing that the majority of the kernel uses is > not usually acceptable. > > IMO, you need some sort of justification why runtime pm is not > applicable for you, because I'm willing to bet Mani/Greg are going to > ask the same. I think we can look at the patch as simply expanding the scope of what already exists. The client here has been calling mhi_device_get/put/sync APIs to gain device vote and with new features yet to come in, this introductory change is only re-purposing what voting means going forward. i.e. allowing individual bus and device votes. If you're suggesting using runtimePM APIs to replace the newly introduced bus vote, it would be kind of overkill here IMO. Is that what you were getting at? Because currently, we just have controllers use runtimePM and provide callbacks to them. If you have ideas, we can discuss them.