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=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 2277CC3F2D1 for ; Thu, 5 Mar 2020 16:23:31 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id E7C80207FD for ; Thu, 5 Mar 2020 16:23:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="lkQknRzU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E7C80207FD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=94U2tGXtsLShgLkMOVQlakwldWC/7qfky8Pao4cuPsE=; b=lkQknRzUS5nbVk ktto4g/hReaLZdoIsSIWXaCv+fAuG3nAZgZIQRtlvoe0Py5EPdW2bcNAT7CT24SbyHpSQWn09rz22 kSxV6fmpM2QOitfm98chiKb/YsuJsXKx1KH9ejPZSSnEeKCy/4U6JfiS0HE3181Lvf5rpvp1MMFav T41EqrxRE37j4PH3yAM4L80sExD73efLri/Khg9BN/LevjrZgEHXO50X7WwhkhbhQK92z5iE/KRty JzjJ0v9gkPICRCr9Sr0vEYH6MVmNubA0dLexEC19vCPuX52N+FPC0pIBIT/lT7BLKFzweItoTxkm5 s8YChUI0SPZXveSzx1ug==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j9tHV-0000KI-J1; Thu, 05 Mar 2020 16:23:29 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1j9tHR-0000Je-MH for linux-arm-kernel@lists.infradead.org; Thu, 05 Mar 2020 16:23:27 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1B16D30E; Thu, 5 Mar 2020 08:23:25 -0800 (PST) Received: from bogus (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 8755F3F534; Thu, 5 Mar 2020 08:23:23 -0800 (PST) Date: Thu, 5 Mar 2020 16:23:21 +0000 From: Sudeep Holla To: Ulf Hansson Subject: Re: [PATCH v2 4/4] cpuidle: psci: Allow WFI to be the only state for the hierarchical topology Message-ID: <20200305162321.GB53631@bogus> References: <20200303203559.23995-1-ulf.hansson@linaro.org> <20200303203559.23995-5-ulf.hansson@linaro.org> <20200304122312.GE25004@bogus> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200305_082325_817561_83343D8C X-CRM114-Status: GOOD ( 34.45 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Lorenzo Pieralisi , Benjamin Gaignard , Linux PM , Stephen Boyd , Daniel Lezcano , "Rafael J . Wysocki" , Lina Iyer , Bjorn Andersson , Sudeep Holla , Linux ARM Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Thu, Mar 05, 2020 at 03:17:42PM +0100, Ulf Hansson wrote: > On Wed, 4 Mar 2020 at 13:23, Sudeep Holla wrote: > > > > The $subject is bit confusing. IIUC, if there are no idle states to > > manage including hierarchical domain states you will not register the driver > > right ? If so, you are not allowing WFI to be the only state, hence my > > concern with $subject. > > I agree that's not so clear, but it wasn't easy to fit everything I > wanted to say in one line. :-) > No worries, just wanted to clarified. Looking at the patch, lot of things got clarified but thought we can always improve. > Is this below better and okay for you? > > "cpuidle: psci: Update condition when avoiding driver registration". > Definitely better than $subject :) > > > > On Tue, Mar 03, 2020 at 09:35:59PM +0100, Ulf Hansson wrote: > > > It's possible that only the WFI state is supported for the CPU, while also > > > a shared idle state exists for a group of CPUs. > > > > > > When the hierarchical topology is used, the shared idle state may not be > > > compatible with arm,idle-state, rather with "domain-idle-state", which > > > makes dt_init_idle_driver() to return zero. This leads to that the > > > cpuidle-psci driver bails out during initialization, avoiding to register a > > > cpuidle driver and instead relies on the default architectural back-end > > > (called via cpu_do_idle()). In other words, the shared idle state becomes > > > unused. > > > > > > Let's fix this behaviour, by allowing the dt_init_idle_driver() to return 0 > > > and then continue with the initialization. If it turns out that the > > > hierarchical topology is used and we have some additional states to manage, > > > then continue with the cpuidle driver registration, otherwise bail out as > > > before. > > > > > > Reported-by: Benjamin Gaignard > > > Fixes: a65a397f2451 ("cpuidle: psci: Add support for PM domains by using genpd") > > > Signed-off-by: Ulf Hansson > > > --- > > > > > > Changes in v2: > > > - Convert the error code returned from psci_cpu_suspend_enter() into an > > > expected error code by cpuidle core. > > > > > > --- > > > drivers/cpuidle/cpuidle-psci.c | 48 +++++++++++++++++++++------------- > > > 1 file changed, 30 insertions(+), 18 deletions(-) > > > > > > diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c > > > index bae9140a65a5..ae0fabec2742 100644 > > > --- a/drivers/cpuidle/cpuidle-psci.c > > > +++ b/drivers/cpuidle/cpuidle-psci.c > > > @@ -56,16 +56,19 @@ static int psci_enter_domain_idle_state(struct cpuidle_device *dev, > > > u32 *states = data->psci_states; > > > struct device *pd_dev = data->dev; > > > u32 state; > > > - int ret; > > > + int ret = 0; > > > > > > /* Do runtime PM to manage a hierarchical CPU toplogy. */ > > > pm_runtime_put_sync_suspend(pd_dev); > > > > > > state = psci_get_domain_state(); > > > - if (!state) > > > + if (!state && states) > > > state = states[idx]; > > > > > > - ret = psci_enter_state(idx, state); > > > + if (state) > > > + ret = psci_cpu_suspend_enter(state) ? -1 : idx; > > > + else > > > + cpu_do_idle(); > > > > May be, I haven't followed this completely yet, but I don't want to be > > in the position to replicated default arch idle hook. Just use the one > > that exist by simply not registering the driver. > > That doesn't work for the configuration I am solving. > > Assume this scenario: We have WFI and a domain/cluster idle state. > From the cpuidle governor point of view, it always selects the WFI > state, which means idx is zero. > OK. The only state that cluster can enter when CPUs are in WFI are cluster WFI and most hardware can handle it automatically. I don't see the need to do any extra work for that. > Then, after we have called pm_runtime_put_sync_suspend() a few lines > above, we may potentially have a "domain state" to use, instead of the > WFI state. > Are they any platforms with this potential "domain state" to use with CPU WFI. I want to understand this better. > In this case, if we would have called psci_enter_state(), that would > lead us to calling cpu_do_idle() from the __CPU_PM_CPU_IDLE_ENTER() > macro, becuase idx is zero. In other words, the domain state would > become unused. > For a domain state to become unused with WFI, it needs to be available and I am not 100% sure of that. > Hope this clarifies what goes on here? > Yes. -- Regards, Sudeep _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel