From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E56213769F7; Tue, 21 Jul 2026 13:53:18 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784642000; cv=none; b=HWJiF03jF4I7nzQzPHtSXyP+oER19vE6bPeZNvgpTnkHB1S19WqYMdVd9MXbnHNk08KvDKLGIVD56bXnL96ZdA8JOP2NYO+5ptQYh9MdjkLxLg86JGycaZvAJ9hSIr8YgqFVuU3pfL4RYc6eQH3/nZ+ybqad9weLq1oeB90XvFY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784642000; c=relaxed/simple; bh=+udyjfrGMyD9vH3/wLeIvE01TbNr7hJTnn0awv3Cat0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=nM55bl6fYykJYn9c20+d7wh0LWbhIpIm7Ll0lvWDfzOoeuPUkk2VqJh/J5M11vgIPRh5W0U5iqzpF2r9LrmVgtb3Kxj0EERreamPvIRNyv8HJVaPj365OJmI63B/f9XBl9EOpufosL88XfrQQ7lx4/tL8fc6jAjssQsNe7o36lM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IxHQZAOP; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="IxHQZAOP" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64DEB1F00A3A; Tue, 21 Jul 2026 13:53:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784641998; bh=Mt8faBpMB1IIl9+TZM5ARhnba5LkjGMQeGNB0pc/k+E=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=IxHQZAOPNrAexzugCNFJxfW8YmvcPLCPNy38A7L9/Y+4Avd91FbCMriUf8SHT9K+v wKoQP3TkufZuP+MOv8VbGzsdrAROCacst+2UvFQUbbx7TrEgsVcQ12de91xlzkaNfP UWCBhAyXEccVfIyAF8gocZHBLz0vqID+vLqooy8AgxWH1RVLXQxOTWFRUPxJiBpX47 2Sq2MmJ9TKNZUg2m1eC7DBS1VEq+mFAqLgjvFHGm+8XgTvU/mF7WNCa87f7bM1Nykx Fv9HoIOx4O/YGkgZWPfGLIflKljmkz8Ab7NhhS3WF6mefnWzPb3tgxOitXq5qOkCTi KtV9RyP+GC1iw== Date: Tue, 21 Jul 2026 14:53:14 +0100 From: Sudeep Holla To: Sneh Mankad Cc: Mark Rutland , Thomas Gleixner , Sudeep Holla , Daniel Lezcano , Peter Zijlstra , "Rafael J. Wysocki" , Pavel Machek , Len Brown , Catalin Marinas , Will Deacon , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH v2] arm64: Disallow disabling boot CPU based on config Message-ID: <20260721-wandering-romantic-buffalo-ebbc4f@sudeepholla> References: <20260703-disable_boot_cpu_offline-v2-1-782d16ff58c3@oss.qualcomm.com> 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: On Tue, Jul 21, 2026 at 02:04:05PM +0100, Mark Rutland wrote: > On Tue, Jul 21, 2026 at 12:29:54PM +0530, Sneh Mankad wrote: > > On 03-Jul-26 7:58 PM, Mark Rutland wrote: > > > On Fri, Jul 03, 2026 at 04:50:02PM +0530, Sneh Mankad wrote: > > > > FW permits CPU0 disablement because it functions properly in regular run time. > > But there is an additional hardware constraint in above mentioned platforms, that > > suspend to ram has to be performed via boot CPU / CPU0. Due to this constraint, > > CPU0 is required to be online when suspend to ram is triggered. > > The PSCI spec doesn't permit that. > > Even if HW has that constraint, it's up to FW to hide that from the OS. > > [...] > > > > This is a platform-specific property, and it's possible to build a > > > kernel that boots on this platform and/or other platforms. > > > > Yes, but for that reason the config will only be enabled for SoCs that have this > > constraint, it will remain disabled for other SoCs. > > Please re-read what I said. A config option can't help if you have a > single kernel that supports multiple platforms. > +1 > > As mentioned above, its not a FW bug. CPU0 is allowed to be disabled > > from FW and HW constraint is for suspend to ram to be performed on > > boot CPU. > > Please see my other reply at: > > https://lore.kernel.org/linux-arm-kernel/al9tdvOxYb83zBxd@J2N7QTR9R3.cambridge.arm.com/T/#m872da3cc4ded3386dce92d4bd4bdf9c33d3e2d0b > > This is *definitely* a firmware bug. > > To be clear, I'm not saying we can't do something to address that, but > let's not pretend that this is compliant with the PSCI spec. > +1 Just curious if CPU_OFF on this CPU0 returns DENIED or just proceeds and ends up with cpu and/or system hang ? -- Regards, Sudeep