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 23AC5C25B48 for ; Tue, 24 Oct 2023 13:07:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234691AbjJXNH5 (ORCPT ); Tue, 24 Oct 2023 09:07:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46134 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343862AbjJXNHq (ORCPT ); Tue, 24 Oct 2023 09:07:46 -0400 Received: from mx.kernkonzept.com (serv1.kernkonzept.com [IPv6:2a01:4f8:1c1c:b490::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EC173D79; Tue, 24 Oct 2023 06:07:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=kernkonzept.com; s=mx1; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Content-Transfer-Encoding:Reply-To: Content-ID:Content-Description; bh=C0NEbr2Bu1GmyIhx8+vqJqdrFza7J7tVm5zNmo+rtEM=; b=ADmrSkg2+Vo/nMsjS9JnEWQIXA qnIPxpsVa5vX7hU+d2iFiLkMCbCus5t3gQGnyi/Gna15ztciE7bHOxhxrsXZaUV/2TeSYz1WMSsYD kxPy56li/HGPSAwcHTe4xw85iNjin0Zjh2I+PyE4IfCYnAXr5/pey5fxNFQ5k10fqmdKQQHZouWJL 91VwJaUsi1eW8Q9gNB4QAWNxAOaU4S8gF4clamZmBpWYe/3x0cQ+P9Fc0x5C2V8luReOAN9Z/4DUI +MQno+CJaHqrMc2o0/48DLGBKayjODFol44/kHZYXjfhJgx5d1luLDZN+XjrVUsmLRSReydprX5iA QmAY6MjQ==; Received: from [10.22.3.24] (helo=kernkonzept.com) by mx.kernkonzept.com with esmtpsa (TLS1.3:ECDHE_X25519__RSA_PSS_RSAE_SHA256__AES_256_GCM:256) (Exim 4.96) id 1qvH7k-000kF4-06; Tue, 24 Oct 2023 15:07:07 +0200 Date: Tue, 24 Oct 2023 15:07:02 +0200 From: Stephan Gerhold To: Ulf Hansson Cc: Viresh Kumar , Andy Gross , Bjorn Andersson , Konrad Dybcio , Ilia Lin , "Rafael J. Wysocki" , Rob Herring , Krzysztof Kozlowski , Conor Dooley , linux-pm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, Stephan Gerhold , stable@vger.kernel.org Subject: Re: [PATCH v2 2/3] cpufreq: qcom-nvmem: Enable virtual power domain devices Message-ID: References: <20231018-msm8909-cpufreq-v2-0-0962df95f654@kernkonzept.com> <20231018-msm8909-cpufreq-v2-2-0962df95f654@kernkonzept.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Tue, Oct 24, 2023 at 02:49:32PM +0200, Ulf Hansson wrote: > On Tue, 24 Oct 2023 at 14:03, Stephan Gerhold > wrote: > > > > On Thu, Oct 19, 2023 at 01:26:19PM +0200, Ulf Hansson wrote: > > > On Thu, 19 Oct 2023 at 12:24, Ulf Hansson wrote: > > > > > > > > On Wed, 18 Oct 2023 at 10:06, Stephan Gerhold > > > > wrote: > > > > > > > > > > The genpd core caches performance state votes from devices that are > > > > > runtime suspended as of commit 3c5a272202c2 ("PM: domains: Improve > > > > > runtime PM performance state handling"). They get applied once the > > > > > device becomes active again. > > > > > > > > > > To attach the power domains needed by qcom-cpufreq-nvmem the OPP core > > > > > calls genpd_dev_pm_attach_by_id(). This results in "virtual" dummy > > > > > devices that use runtime PM only to control the enable and performance > > > > > state for the attached power domain. > > > > > > > > > > However, at the moment nothing ever resumes the virtual devices created > > > > > for qcom-cpufreq-nvmem. They remain permanently runtime suspended. This > > > > > means that performance state votes made during cpufreq scaling get > > > > > always cached and never applied to the hardware. > > > > > > > > > > Fix this by enabling the devices after attaching them and use > > > > > dev_pm_syscore_device() to ensure the power domains also stay on when > > > > > going to suspend. Since it supplies the CPU we can never turn it off > > > > > from Linux. There are other mechanisms to turn it off when needed, > > > > > usually in the RPM firmware (RPMPD) or the cpuidle path (CPR genpd). > > > > > > > > I believe we discussed using dev_pm_syscore_device() for the previous > > > > version. It's not intended to be used for things like the above. > > > > > > > > Moreover, I was under the impression that it wasn't really needed. In > > > > fact, I would think that this actually breaks things for system > > > > suspend/resume, as in this case the cpr driver's genpd > > > > ->power_on|off() callbacks are no longer getting called due this, > > > > which means that the cpr state machine isn't going to be restored > > > > properly. Or did I get this wrong? > > > > > > BTW, if you really need something like the above, the proper way to do > > > it would instead be to call device_set_awake_path() for the device. > > > > > > > Unfortunately this does not work correctly. When I use > > device_set_awake_path() it does set dev->power.wakeup_path = true. > > However, this flag is cleared again in device_prepare() when entering > > suspend. To me it looks a bit like wakeup_path is not supposed to be set > > directly by drivers? Before and after your commit 8512220c5782 ("PM / > > core: Assign the wakeup_path status flag in __device_prepare()") it > > seems to be internally bound to device_may_wakeup(). > > > > It works if I make device_may_wakeup() return true, with > > > > device_set_wakeup_capable(dev, true); > > device_wakeup_enable(dev); > > > > but that also allows *disabling* the wakeup from sysfs which doesn't > > really make sense for the CPU. > > > > Any ideas? > > The device_set_awake_path() should be called from a system suspend > callback. So you need to add that callback for the cpufreq driver. > > Sorry, if that wasn't clear. > Hmm, but at the moment I'm calling this on the virtual genpd devices. How would it work for them? I don't have a suspend callback for them. I guess could loop over the virtual devices in the cpufreq driver suspend callback, but is my driver suspend callback really guaranteed to run before the device_prepare() that clears "wakeup_path" on the virtual devices? Or is this the point where we need device links to make that work? A quick look suggests "wakeup_path" is just propagated to parents but not device links, so I don't think that would help, either. Thanks, -- Stephan Gerhold Kernkonzept GmbH at Dresden, Germany, HRB 31129, CEO Dr.-Ing. Michael Hohmuth