From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org,
linux-kernel@vger.kernel.org
Cc: f.fainelli@gmail.com, arnd@arndb.de, narmstrong@baylibre.com,
dwmw2@infradead.org, linux@armlinux.org.uk, hch@infradead.org,
will@kernel.org, robh+dt@kernel.org, catalin.marinas@arm.com,
robin.murphy@arm.com, ardb@kernel.org,
Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Subject: [RFC 00/13] Generic way of dealing with broken 64-bit buses
Date: Fri, 26 Feb 2021 15:02:52 +0100 [thread overview]
Message-ID: <20210226140305.26356-1-nsaenzjulienne@suse.de> (raw)
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(-)
--
2.30.1
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next reply other threads:[~2021-02-26 14:05 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 14:02 Nicolas Saenz Julienne [this message]
2021-02-26 14:02 ` [RFC 01/13] dt-bindings: Introduce 64bit-mmio-broken Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 02/13] driver core: Introduce MMIO configuration Nicolas Saenz Julienne
2021-03-02 11:29 ` Robin Murphy
2021-03-02 14:09 ` Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 03/13] of: device: Introduce of_mmio_configure() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 04/13] driver core: plafrom: Introduce platform_mmio_configure() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 05/13] pci: Introduce pci_mmio_configure() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 06/13] device core: Introduce dev_64bit_mmio_supported() Nicolas Saenz Julienne
2021-02-26 14:02 ` [RFC 07/13] arm64: Mark ARCH_MVEBU as needing broken 64bit MMIO support Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 08/13] arm64: dts: marvell: armada-ap80x: Mark config-space bus as 64bit-mmio-broken Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 09/13] iommu/arm-smmu: Make use of dev_64bit_mmio_supported() Nicolas Saenz Julienne
2021-03-02 9:32 ` Arnd Bergmann
2021-03-02 12:42 ` Nicolas Saenz Julienne
2021-03-02 11:07 ` Robin Murphy
2021-03-02 13:38 ` Nicolas Saenz Julienne
2021-03-03 8:44 ` Arnd Bergmann
2021-02-26 14:03 ` [RFC 10/13] iommu/arm-smmu-impl: Get rid of Marvell's implementation details Nicolas Saenz Julienne
2021-03-02 11:40 ` Robin Murphy
2021-03-02 14:06 ` Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 11/13] arm64: Mark ARCH_BCM2835 as needing broken 64bit MMIO support Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 12/13] ARM: dts: bcm2711: Mark PCIe bus as 64bit-mmio-broken Nicolas Saenz Julienne
2021-02-26 14:03 ` [RFC 13/13] scsi: megaraid: Make use of dev_64bit_mmio_supported() Nicolas Saenz Julienne
2021-02-26 14:30 ` Arnd Bergmann
2021-02-26 18:06 ` Arnd Bergmann
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