From patchwork Thu Dec 13 17:59:52 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Russell King (Oracle)" X-Patchwork-Id: 10729407 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 378BB13BF for ; Thu, 13 Dec 2018 18:00:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 259C12C7D0 for ; Thu, 13 Dec 2018 18:00:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 17BB02C803; Thu, 13 Dec 2018 18:00:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.7 required=2.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 36DC32C7D0 for ; Thu, 13 Dec 2018 18:00:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728128AbeLMSAK (ORCPT ); Thu, 13 Dec 2018 13:00:10 -0500 Received: from pandora.armlinux.org.uk ([78.32.30.218]:50960 "EHLO pandora.armlinux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727618AbeLMSAK (ORCPT ); Thu, 13 Dec 2018 13:00:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=armlinux.org.uk; s=pandora-2014; h=Sender:Content-Type:MIME-Version: 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:In-Reply-To:References:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=IVB28Db9ZKXqdHKKo03v707cx3bqKns8Z36Y8D2nxKo=; b=XCLNhu4n9w/9bFuyRnjjDuhdS 1/0Qiy+5ruIfFQs4mkW7H7lqpSBUXBc+NnrE4hgmCj+LqYBw8nITtieuKU+gc6xun1xT2zeZNQLLY LfiA+3S7VCuMDmw8PGxxBoK3zDWPcI6IaTg60GUClM/qEzaKmQbB5bVfB8SQ8rifQx9AY=; Received: from n2100.armlinux.org.uk ([2001:4d48:ad52:3201:214:fdff:fe10:4f86]:37583) by pandora.armlinux.org.uk with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.90_1) (envelope-from ) id 1gXVHA-0003rL-NP; Thu, 13 Dec 2018 17:59:56 +0000 Received: from linux by n2100.armlinux.org.uk with local (Exim 4.90_1) (envelope-from ) id 1gXVH8-0000ku-58; Thu, 13 Dec 2018 17:59:54 +0000 Date: Thu, 13 Dec 2018 17:59:52 +0000 From: Russell King - ARM Linux To: linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-omap@vger.kernel.org, linux-oxnas@groups.io, linux-samsung-soc@vger.kernel.org, linux-soc@vger.kernel.org Cc: Andreas =?iso-8859-1?q?F=E4rber?= , Andy Gross , Barry Song , David Brown , Krzysztof Kozlowski , Kukjin Kim , Linus Walleij , Liviu Dudau , Lorenzo Pieralisi , Manivannan Sadhasivam , Neil Armstrong , Patrice Chotard , Shiraz Hashim , Sudeep Holla , Tony Lindgren , Viresh Kumar Subject: [PATCH 0/9] Clean up ARM SMP/CPU hotplug implementations Message-ID: <20181213175952.GC26090@n2100.armlinux.org.uk> MIME-Version: 1.0 Content-Disposition: inline User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP There is a lot of apparent copied code in arch/arm for handling SMP/ CPU hotplug, much of which is inappropriate or plain buggy. This seems to be a topic that occasionally comes up. The "pen_release" thing was created for ARM Ltd development platforms where there was no way to individually control secondary CPUs leaving the boot loader - they all jumped to whatever physical code address was supplied at the same time. This made it necessary for _these_ platforms to have a "holding pen" for the CPUs while the kernel initialised. The "boot_lock" thing was also created for ARM Ltd development platforms which had restricted bus bandwidth, and which used the loops_per_jiffy delay mechanism, which was calibrated for each secondary CPU. With the restricted bus bandwidth, activity from the boot CPU would affect the delay calibration adversely. Lastly, the Versatile CPU hotplug implementation is an entirely ficticious one - these platforms do _not_ support CPU hotplug as there is no way to actually disable any of the secondary CPUs, or reset them. Such an implementation is not acceptable when supporting features such as suspend or kexec. As the Versatile platforms are ARM development platforms which do not have suspend support, this is acceptable there, but not for production hardware. None of these three facilities/implementations should be used on modern production hardware, yet we have a number of copies of this code. This series addresses that by removing the inappropriate copies of some Realview/Versatile Express specific workarounds, and makes it (hopefully) more clear that introducing this code is really not acceptable. To discourage copying the Versatile code, further comments are added and the functions renamed for CPU hotplug to be "immitation" to make it clear that it's not a real implementation. We tried reducing the duplication in the past with ideas around consolidating the pen_release/boot_lock/immitation hotplug stuff, but I nacked that because it's not an acceptable implementation for production hardware. However, we did decide to consolidate the "pen_release" definition. In hind sight, that was a mistake, because that gave more credence to that way of doing things, and also gave rise to buggy implementations which only read from that variable - meaning it served no useful purpose. There are some rather complex cases that remain, and those need the SoC folk to fix. I have left the Actions Semi patch in place since following patches depend on it, but there is a five-patch series from Linus Walleij that address this platform which should replace this patch - with the patch concerned marked as "RFT" - request for testing. arch/arm/include/asm/smp.h | 1 - arch/arm/kernel/smp.c | 6 -- arch/arm/mach-actions/platsmp.c | 15 --- arch/arm/mach-exynos/headsmp.S | 2 +- arch/arm/mach-exynos/platsmp.c | 31 +++--- arch/arm/mach-omap2/omap-smp.c | 20 ---- arch/arm/mach-oxnas/Makefile | 1 - arch/arm/mach-oxnas/hotplug.c | 109 -------------------- arch/arm/mach-oxnas/platsmp.c | 4 - arch/arm/mach-prima2/common.h | 2 + arch/arm/mach-prima2/headsmp.S | 2 +- arch/arm/mach-prima2/hotplug.c | 3 +- arch/arm/mach-prima2/platsmp.c | 17 ++-- arch/arm/mach-qcom/platsmp.c | 26 ----- arch/arm/mach-realview/Makefile | 1 - arch/arm/mach-realview/hotplug.c | 111 --------------------- arch/arm/mach-realview/hotplug.h | 1 - arch/arm/mach-realview/platsmp-dt.c | 8 +- arch/arm/mach-spear/generic.h | 2 + arch/arm/mach-spear/headsmp.S | 2 +- arch/arm/mach-spear/hotplug.c | 4 +- arch/arm/mach-spear/platsmp.c | 27 +++-- arch/arm/mach-sti/Makefile | 2 +- arch/arm/mach-sti/headsmp.S | 43 -------- arch/arm/mach-sti/platsmp.c | 62 +----------- arch/arm/mach-vexpress/Makefile | 1 - arch/arm/mach-vexpress/core.h | 2 - arch/arm/mach-vexpress/platsmp.c | 7 ++ arch/arm/plat-versatile/Makefile | 1 + arch/arm/plat-versatile/headsmp.S | 2 +- .../{mach-vexpress => plat-versatile}/hotplug.c | 47 ++++----- arch/arm/plat-versatile/include/plat/platsmp.h | 2 + arch/arm/plat-versatile/platsmp.c | 47 ++++++--- 33 files changed, 132 insertions(+), 479 deletions(-) delete mode 100644 arch/arm/mach-oxnas/hotplug.c delete mode 100644 arch/arm/mach-realview/hotplug.c delete mode 100644 arch/arm/mach-realview/hotplug.h delete mode 100644 arch/arm/mach-sti/headsmp.S rename arch/arm/{mach-vexpress => plat-versatile}/hotplug.c (56%)