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 F29B4C433F5 for ; Thu, 3 Feb 2022 18:53:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1353583AbiBCSxL (ORCPT ); Thu, 3 Feb 2022 13:53:11 -0500 Received: from foss.arm.com ([217.140.110.172]:36530 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233247AbiBCSxK (ORCPT ); Thu, 3 Feb 2022 13:53:10 -0500 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 C7B24147A; Thu, 3 Feb 2022 10:53:09 -0800 (PST) Received: from bogus (unknown [10.57.41.150]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5A0423F774; Thu, 3 Feb 2022 10:53:08 -0800 (PST) Date: Thu, 3 Feb 2022 18:52:21 +0000 From: Sudeep Holla To: Florian Fainelli Cc: linux-arm-kernel@lists.infradead.org, "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" , Mark Rutland , Sudeep Holla , Lorenzo Pieralisi , open list Subject: Re: [PATCH 0/4] Broadcom STB PM PSCI extensions Message-ID: <20220203185221.aw7kayj6qklmh5is@bogus> References: <20220122035421.4086618-1-f.fainelli@gmail.com> <20220203111435.e3eblv47ljkwkvwf@bogus> <34938793-cecc-2ad8-a4eb-81bb278ce9b5@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <34938793-cecc-2ad8-a4eb-81bb278ce9b5@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Correction: it is known as "freeze" rather than "idle" in terms of values as per /sys/power/state. Sorry for referring it as "idle" and creating any confusion. On Thu, Feb 03, 2022 at 09:36:28AM -0800, Florian Fainelli wrote: > > > On 2/3/2022 3:14 AM, Sudeep Holla wrote: > > On Fri, Jan 21, 2022 at 07:54:17PM -0800, Florian Fainelli wrote: > > > Hi all, > > > > > > This patch series contains the Broadcom STB PSCI extensions which adds > > > some additional functions on top of the existing standard PSCI interface > > > which is the reason for having the driver implement a custom > > > suspend_ops. > > > > > > These platforms have traditionally supported a mode that is akin to > > > ACPI's S2 with the CPU in WFI and all of the chip being clock gated > > > which is entered with "echo standby > /sys/power/state". Additional a > > > true suspend to DRAM as defined in ACPI by S3 is implemented with "echo > > > mem > /sys/power/state". > > > > How different is the above "standby" state compare to the standard "idle" > > (a.k.a suspend-to-idle which is different from system-to-ram/S3) ? > > There are a few differences: > > - s2idle does not power gate the secondary CPUs > Not sure what you mean by that ? S2I takes CPUs to deepest idle state. If you want shallower states, one possible option is the disable deeper states from the userspace. > - s2idle requires the use of in-band interrupts for wake-up > I am not sure if that is true. S2I behaves very similar to S2R except it has low wake latency as all secondaries CPUs are not hotplugged out. > The reasons for implementing "standby" are largely two fold: > > - we need to achieve decent power savings (typically below 0.5W for the > whole system while allowing Wake-on-WLAN, GPIO, RTC, infrared, etc.) > I fail to understand how that is a problem from S2I. It is probably worth checking if there are any unnecessary IRQF_NO_SUSPEND users. Check section IRQF_NO_SUSPEND and enable_irq_wake() in [1]. I don't see any issues other wise in terms of unnecessary/spurious wakeup by in-band(to be precise no-wake up) interrupts. > - we have a security subsystem that requires the CPUs to be either power > gated or idle in order the hardware state machine that lets the system enter > such a state and allows the out of band interrupts from being wake-up > sources > It should work unless I have completely misunderstood how S2I works. > > Suspend to idle takes all the CPUs to lowest possible power state instead > > of cpu-hotplug in S2R. Also I assume some userspace has to identify when > > to enter "standby" vs "mem" right ? I am trying to see how addition of > > "idle" changes that(if it does). Sorry for too many questions. > > > > Right that user-space in our case is either custom (like RDK, or completely > custom), or is Android. For Android it looks like we are carrying a patch > that makes "mem" de-generate into "standby" but this is largely because we > had historically problems with "mem" that are being addressed (completely > orthogonal). > Thanks for the info. > I did not consider it as a viable option at the time, but if we were to > implement "standby" in drivers/firmware/psci/psci.c would that be somewhat > acceptable? > We have been pointing anyone needing standby so far to S2I and so far no one has shouted that it doesn't suffice. Let me know what is missing. -- Regards, Sudeep [1] Documentation/power/suspend-and-interrupts.rst 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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 515EAC433F5 for ; Thu, 3 Feb 2022 18:54:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc: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=aVZ+TjVJIs7/3DaFqmFf32ACY6R+G+5q20cU+q3FoI4=; b=jOUBwzkFwj8rfY l7o6SXNpn0uNC9djCWV40aOTUfBefZYKiqtm5u7O6Y+SVn3/QDF+tmDkvsL014lbHhh2PJO36pLzo OndRpIGoze2WZm5FbZJYXc2+I/uNrDTXmmZAKtibtTAVpvpxpO0Sz9vRGAY6fEqkPkGvUhlGj7P1z YpJhcOhHOJa+5qofg7Z+N2904CuVSH464XedBbcbnXe8ghbqi6wcSX7BMUs5oSV5zSIPdwnnwIetm 28b1nYVmMlQ2vQVlkKmHXDeXM1cew29K/pR0LXsvap5dsoBn4i4vLviM6uDrUpIn8CRJ6TbayS3Jm DeDGmtnPsPVY3hxiiADA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nFhEJ-002Xuf-BT; Thu, 03 Feb 2022 18:53:15 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nFhEF-002XtP-4k for linux-arm-kernel@lists.infradead.org; Thu, 03 Feb 2022 18:53:12 +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 C7B24147A; Thu, 3 Feb 2022 10:53:09 -0800 (PST) Received: from bogus (unknown [10.57.41.150]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5A0423F774; Thu, 3 Feb 2022 10:53:08 -0800 (PST) Date: Thu, 3 Feb 2022 18:52:21 +0000 From: Sudeep Holla To: Florian Fainelli Cc: linux-arm-kernel@lists.infradead.org, "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" , Mark Rutland , Sudeep Holla , Lorenzo Pieralisi , open list Subject: Re: [PATCH 0/4] Broadcom STB PM PSCI extensions Message-ID: <20220203185221.aw7kayj6qklmh5is@bogus> References: <20220122035421.4086618-1-f.fainelli@gmail.com> <20220203111435.e3eblv47ljkwkvwf@bogus> <34938793-cecc-2ad8-a4eb-81bb278ce9b5@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <34938793-cecc-2ad8-a4eb-81bb278ce9b5@gmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220203_105311_301226_6F4E8C8F X-CRM114-Status: GOOD ( 33.57 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Correction: it is known as "freeze" rather than "idle" in terms of values as per /sys/power/state. Sorry for referring it as "idle" and creating any confusion. On Thu, Feb 03, 2022 at 09:36:28AM -0800, Florian Fainelli wrote: > > > On 2/3/2022 3:14 AM, Sudeep Holla wrote: > > On Fri, Jan 21, 2022 at 07:54:17PM -0800, Florian Fainelli wrote: > > > Hi all, > > > > > > This patch series contains the Broadcom STB PSCI extensions which adds > > > some additional functions on top of the existing standard PSCI interface > > > which is the reason for having the driver implement a custom > > > suspend_ops. > > > > > > These platforms have traditionally supported a mode that is akin to > > > ACPI's S2 with the CPU in WFI and all of the chip being clock gated > > > which is entered with "echo standby > /sys/power/state". Additional a > > > true suspend to DRAM as defined in ACPI by S3 is implemented with "echo > > > mem > /sys/power/state". > > > > How different is the above "standby" state compare to the standard "idle" > > (a.k.a suspend-to-idle which is different from system-to-ram/S3) ? > > There are a few differences: > > - s2idle does not power gate the secondary CPUs > Not sure what you mean by that ? S2I takes CPUs to deepest idle state. If you want shallower states, one possible option is the disable deeper states from the userspace. > - s2idle requires the use of in-band interrupts for wake-up > I am not sure if that is true. S2I behaves very similar to S2R except it has low wake latency as all secondaries CPUs are not hotplugged out. > The reasons for implementing "standby" are largely two fold: > > - we need to achieve decent power savings (typically below 0.5W for the > whole system while allowing Wake-on-WLAN, GPIO, RTC, infrared, etc.) > I fail to understand how that is a problem from S2I. It is probably worth checking if there are any unnecessary IRQF_NO_SUSPEND users. Check section IRQF_NO_SUSPEND and enable_irq_wake() in [1]. I don't see any issues other wise in terms of unnecessary/spurious wakeup by in-band(to be precise no-wake up) interrupts. > - we have a security subsystem that requires the CPUs to be either power > gated or idle in order the hardware state machine that lets the system enter > such a state and allows the out of band interrupts from being wake-up > sources > It should work unless I have completely misunderstood how S2I works. > > Suspend to idle takes all the CPUs to lowest possible power state instead > > of cpu-hotplug in S2R. Also I assume some userspace has to identify when > > to enter "standby" vs "mem" right ? I am trying to see how addition of > > "idle" changes that(if it does). Sorry for too many questions. > > > > Right that user-space in our case is either custom (like RDK, or completely > custom), or is Android. For Android it looks like we are carrying a patch > that makes "mem" de-generate into "standby" but this is largely because we > had historically problems with "mem" that are being addressed (completely > orthogonal). > Thanks for the info. > I did not consider it as a viable option at the time, but if we were to > implement "standby" in drivers/firmware/psci/psci.c would that be somewhat > acceptable? > We have been pointing anyone needing standby so far to S2I and so far no one has shouted that it doesn't suffice. Let me know what is missing. -- Regards, Sudeep [1] Documentation/power/suspend-and-interrupts.rst _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel