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 F3A00C87FCF for ; Wed, 13 Aug 2025 12:13:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mpjggtp7GwhS048QoCuCUNA/NXXIWIBRizdSAeH+gKI=; b=cXjhjxeWPTOvNej4/ZiBHQ010W Gw3CsJhScbmCNHD80B1wYsIoVDOMCcwlvaR2BbpO7/FxKa2lmNvBKjytHby9XSGuuGEucHN0KuyaX mQQHPZThzfoAmrIh16uWEhk592uXkAlQxC2dSKCXo+4/oUZv1DeKVEGN+yBK8bpGbstvCez/5JsYi HKQKpNQuep/bJdaS5qclzwygSTOHvi6gp3YKzPh/Vhw3JrArMGizVDsTs+xO1n/5ZEoe4E4C0imhm 4TTwOJBJHv1jQureNW6aqmXPs+fdV8FnZ+5wtWzbSMaTg7vpzjJgxVsIZFKmilh+kq6BcSEOOtbRX hidYcKgw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1umALn-0000000Dc5i-0bhk; Wed, 13 Aug 2025 12:13:03 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1um9lc-0000000DX2Y-1H32 for linux-arm-kernel@lists.infradead.org; Wed, 13 Aug 2025 11:35:41 +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 8F0EF12FC; Wed, 13 Aug 2025 04:35:28 -0700 (PDT) Received: from raptor (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 922E53F738; Wed, 13 Aug 2025 04:35:34 -0700 (PDT) Date: Wed, 13 Aug 2025 12:35:31 +0100 From: Alexandru Elisei To: Sudeep Holla Cc: Marc Zyngier , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Lorenzo Pieralisi , Hanjun Guo , "Rafael J. Wysocki" , Daniel Lezcano , Thomas Gleixner , Mark Rutland , alexandru.elisei@arm.com Subject: Re: [PATCH 0/4] clocksource: Add standalone MMIO ARM arch timer driver Message-ID: References: <20250807160243.1970533-1-maz@kernel.org> <20250813-macho-snobbish-alpaca-ff07fa@sudeepholla> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250813-macho-snobbish-alpaca-ff07fa@sudeepholla> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250813_043540_390123_DFC91346 X-CRM114-Status: GOOD ( 25.60 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hello, On Wed, Aug 13, 2025 at 11:55:48AM +0100, Sudeep Holla wrote: > +Alexandru > > On Thu, Aug 07, 2025 at 05:02:39PM +0100, Marc Zyngier wrote: > > For the past 10 years, both Mark and I have been lamenting about the > > sorry state of the badly named "arch_timer" driver, and about the way > > the MMIO part is intricately weaved into the system-register part. > > > > The time has finally come to have a stab at it. > > > > This small series simply creates a new timer driver for the MMIO arch > > timer, and only that. It is an actual driver, and not some kludge that > > has to run super early (that's what the per-CPU timers are for). This > > allows, in turn, a pretty large cleanup of the per-CPU driver, though > > there is more to come -- one thing at a time. > > > > As an added bonus, we get a clocksource, which the original code > > didn't provide. Just in case it might be useful. The end-result is far > > more readable, and about 100 lines smaller. > > > > (Tested it on Juno R2 and FVP in both DT and ACPI boot) > > Tested-by: Sudeep Holla > Reviewed-by: Sudeep Holla > > Alexandru found it useful(avoids some unexpected hang IIUC) in his setup > based on bootwrapper which doesn't initialise MMIO timers. Just FYI, this is the testing that I did. Without this series, if firmware (boot-wrapper-aarch64 in my testing) doesn't configure access to the memory-mapped timer: [ 0.000000] arch_timer: Unable to find a suitable frame in timer @ 0x000000002a810000 [ 0.000000] Failed to initialize '/timer@2a810000': -22 .. [ 0.528000] kvm [1]: kvm_arch_timer: uninitialized timecounter .. # ls /dev/kvm ls: cannot access '/dev/kvm': No such file or directory With this series, if firmware doesn't configure access to the memory-mapped timer: [ 0.549399] kvm [1]: Hyp nVHE mode initialized successfully .. [ 2.018050] arch-timer-mmio 2a810000.timer: Unable to find a suitable frame in timer @ 0x000000002a810000 [ 2.018123] arch-timer-mmio 2a810000.timer: probe with driver arch-timer-mmio failed with error -22 .. # ls /dev/kvm /dev/kvm Thanks, Alex