From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8996116FF3B; Tue, 12 Mar 2024 15:57:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710259068; cv=none; b=tEny7+y/TOyiRf94sEyYvhA/DeSnlO8l1yfDUOei427PGRUp86bKgoER/FMjR4QeMen4Ld/Q7RRoBBV4bJ+wDt3yKSx5zT6ZK22YNXRVTpyZHotrK0vfxOmoNTGUTW9jDuNmGU1WWxduXgP/jpk02U0aVIk4EZLRS9Qmbd5M8Gc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710259068; c=relaxed/simple; bh=qHTdrZJMFBSmWNwbyHjOmWb7ZpYhhu2kMlfqSqKfUEs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KfVPWif/5hLh1eZwRayH3q3lKC0h/JtC2u0n2NNk+gl3dQZzVJ9sFWU+PgDWjW+9mviMU5hFW/bjJQQek+jP9FLu8rh21hX9Sf+uBMRvSvGAzrIQ1XEDyoBAQ3QfkFmLvPXryrdcL+1BWmgGLQ1OcNoENtuHjlxc/FWsajPEzak= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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 DE2391007; Tue, 12 Mar 2024 08:58:22 -0700 (PDT) Received: from bogus (e103737-lin.cambridge.arm.com [10.1.197.49]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 558A63F73F; Tue, 12 Mar 2024 08:57:42 -0700 (PDT) Date: Tue, 12 Mar 2024 15:57:39 +0000 From: Sudeep Holla To: David Woodhouse Cc: linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org, Paolo Bonzini , Jonathan Corbet , Marc Zyngier , Sudeep Holla , Oliver Upton , James Morse , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Mark Rutland , Lorenzo Pieralisi , "Rafael J. Wysocki" , Len Brown , Pavel Machek , David Woodhouse , Mostafa Saleh , Jean-Philippe Brucker , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-pm@vger.kernel.org Subject: Re: [RFC PATCH 2/2] arm64: Use SYSTEM_OFF2 PSCI call to power off for hibernate Message-ID: References: <20240312135958.727765-1-dwmw2@infradead.org> <20240312135958.727765-3-dwmw2@infradead.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240312135958.727765-3-dwmw2@infradead.org> On Tue, Mar 12, 2024 at 01:51:29PM +0000, David Woodhouse wrote: > From: David Woodhouse > > The PSCI v1.3 specification (alpha) adds support for a SYSTEM_OFF2 > function which is analogous to ACPI S4 state. This will allow hosting > environments to determine that a guest is hibernated rather than just > powered off, and handle that state appropriately on subsequent launches. > > Since commit 60c0d45a7f7a ("efi/arm64: use UEFI for system reset and > poweroff") the EFI shutdown method is deliberately preferred over PSCI > or other methods. So register a SYS_OFF_MODE_POWER_OFF handler which > *only* handles the hibernation, leaving the original PSCI SYSTEM_OFF as > a last resort via the legacy pm_power_off function pointer. > > The hibernation code already exports a system_entering_hibernation() > function which is be used by the higher-priority handler to check for > hibernation. That existing function just returns the value of a static > boolean variable from hibernate.c, which was previously only set in the > hibernation_platform_enter() code path. Set the same flag in the simpler > code path around the call to kernel_power_off() too. > > An alternative way to hook SYSTEM_OFF2 into the hibernation code would > be to register a platform_hibernation_ops structure with an ->enter() > method which makes the new SYSTEM_OFF2 call. But that would have the > unwanted side-effect of making hibernation take a completely different > code path in hibernation_platform_enter(), invoking a lot of special dpm > callbacks. > > Another option might be to add a new SYS_OFF_MODE_HIBERNATE mode, with > fallback to SYS_OFF_MODE_POWER_OFF. Or to use the sys_off_data to > indicate whether the power off is for hibernation. > > But this version works and is relatively simple. > > Signed-off-by: David Woodhouse > --- > drivers/firmware/psci/psci.c | 35 +++++++++++++++++++++++++++++++++++ > kernel/power/hibernate.c | 5 ++++- > 2 files changed, 39 insertions(+), 1 deletion(-) > > diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c > index d9629ff87861..69d2f6969438 100644 > --- a/drivers/firmware/psci/psci.c > +++ b/drivers/firmware/psci/psci.c > @@ -78,6 +78,7 @@ struct psci_0_1_function_ids get_psci_0_1_function_ids(void) > > static u32 psci_cpu_suspend_feature; > static bool psci_system_reset2_supported; > +static bool psci_system_off2_supported; > > static inline bool psci_has_ext_power_state(void) > { > @@ -333,6 +334,28 @@ static void psci_sys_poweroff(void) > invoke_psci_fn(PSCI_0_2_FN_SYSTEM_OFF, 0, 0, 0); > } > > +#ifdef CONFIG_HIBERNATION > +static int psci_sys_hibernate(struct sys_off_data *data) > +{ > + if (system_entering_hibernation()) > + invoke_psci_fn(PSCI_FN_NATIVE(1_3, SYSTEM_OFF2), > + PSCI_1_3_HIBERNATE_TYPE_OFF, 0, 0); > + return NOTIFY_DONE; > +} > + > +static int __init psci_hibernate_init(void) > +{ > + if (psci_system_off2_supported) { > + /* Higher priority than EFI shutdown, but only for hibernate */ > + register_sys_off_handler(SYS_OFF_MODE_POWER_OFF, > + SYS_OFF_PRIO_FIRMWARE + 2, > + psci_sys_hibernate, NULL); > + } > + return 0; > +} > +subsys_initcall(psci_hibernate_init); Looked briefly at register_sys_off_handler and it should be OK to call it from psci_init_system_off2() below. Any particular reason for having separate initcall to do this ? We can even eliminate the need for psci_init_system_off2 if it can be called from there. What am I missing ? -- Regards, Sudeep