From patchwork Fri Feb 26 14:02:52 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Nicolas Saenz Julienne X-Patchwork-Id: 1444940 Return-Path: X-Original-To: incoming-dt@patchwork.ozlabs.org Delivered-To: patchwork-incoming-dt@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org (client-ip=23.128.96.18; helo=vger.kernel.org; envelope-from=devicetree-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by ozlabs.org (Postfix) with ESMTP id 4DnBHH0gQYz9sVX for ; Sat, 27 Feb 2021 01:04:43 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230006AbhBZOE1 (ORCPT ); Fri, 26 Feb 2021 09:04:27 -0500 Received: from mx2.suse.de ([195.135.220.15]:53378 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229769AbhBZOD7 (ORCPT ); Fri, 26 Feb 2021 09:03:59 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id D6620AF63; Fri, 26 Feb 2021 14:03:15 +0000 (UTC) From: Nicolas Saenz Julienne To: linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Cc: f.fainelli@gmail.com, robh+dt@kernel.org, robin.murphy@arm.com, ardb@kernel.org, hch@infradead.org, narmstrong@baylibre.com, dwmw2@infradead.org, linux@armlinux.org.uk, catalin.marinas@arm.com, arnd@arndb.de, will@kernel.org, Nicolas Saenz Julienne Subject: [RFC 00/13] Generic way of dealing with broken 64-bit buses Date: Fri, 26 Feb 2021 15:02:52 +0100 Message-Id: <20210226140305.26356-1-nsaenzjulienne@suse.de> X-Mailer: git-send-email 2.30.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org BCM2711, Raspberry Pi 4's arm64 system on chip, contains a PCIe bus that can't handle 64-bit accesses to its MMIO address space. The issue has already been discussed here[1], and it turns out BCM2711 isn't the only broken device in the wild. In most cases, the solution to this issue is to convert writeq/readq() to into their lo_hi/hi_lo variants and the eventual introduction of some amount of locking. But that's not good enough for every device. For example, on some arm's SMMU configurations atomic 64-bit accesses are mandatory. This series tries to introduce a mechanism for drivers to be able to ascertain whether or not they are allowed to perform 64-bit accesses. The big question is the amount of granularity needed to deal with this (think here of distro images): - Build-time: if a broken platform included in the image, disallow any 64-bit access. Drivers that need 64-bit accesses could simply bypass the check and hope for the best. Imposes a performance penalty on otherwise well behaving platforms, and features that depend on 64bit access might be disabled unnecessarily. It's simple to implement, yet not very generic/future proof. - Run-time: allow/disallow 64-bit accesses based on boot time checks (i.e. check which platform the kernel is running on). Gets rid of all the negative aspects imposed to well-behaving platforms. Well-behaving buses can't coexist with broken ones while using all features. - Per-device: each device has its MMIO access properties and can take decisions based on its local bus. That said, I'm not aware of a system that absolutely needs this ATM. This series implements the third option mainly as a proof of concept. It's my personal preference on how to deal with this. That said, my main aim ATM is to settle on a general approach. Regards, Nicolas [1] https://lore.kernel.org/linux-arm-kernel/c188698ca0de3ed6c56a0cf7880e1578aa753077.camel@suse.de/ --- Nicolas Saenz Julienne (13): dt-bindings: Introduce 64bit-mmio-broken driver core: Introduce MMIO configuration of: device: Introduce of_mmio_configure() driver core: plafrom: Introduce platform_mmio_configure() pci: Introduce pci_mmio_configure() device core: Introduce dev_64bit_mmio_supported() arm64: Mark ARCH_MVEBU as needing broken 64bit MMIO support arm64: dts: marvell: armada-ap80x: Mark config-space bus as 64bit-mmio-broken iommu/arm-smmu: Make use of dev_64bit_mmio_supported() iommu/arm-smmu-impl: Get rid of Marvell's implementation details arm64: Mark ARCH_BCM2835 as needing broken 64bit MMIO support ARM: dts: bcm2711: Mark PCIe bus as 64bit-mmio-broken scsi: megaraid: Make use of dev_64bit_mmio_supported() .../devicetree/bindings/common-properties.txt | 15 +++++++++++ arch/Kconfig | 8 ++++++ arch/arm/boot/dts/bcm2711.dtsi | 1 + arch/arm64/Kconfig.platforms | 2 ++ arch/arm64/boot/dts/marvell/armada-ap80x.dtsi | 1 + drivers/base/dd.c | 6 +++++ drivers/base/platform.c | 9 +++++++ drivers/iommu/arm/arm-smmu/arm-smmu-impl.c | 21 --------------- drivers/iommu/arm/arm-smmu/arm-smmu.c | 9 +++++++ drivers/iommu/arm/arm-smmu/arm-smmu.h | 9 +++++-- drivers/of/device.c | 19 ++++++++++++++ drivers/pci/pci-driver.c | 26 +++++++++++++++++++ drivers/scsi/megaraid/megaraid_sas_fusion.c | 23 ++++++++-------- include/linux/device.h | 20 ++++++++++++++ include/linux/device/bus.h | 3 +++ include/linux/of_device.h | 8 ++++++ 16 files changed, 145 insertions(+), 35 deletions(-)