From: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
To: Robin Murphy <robin.murphy@arm.com>,
linux-arm-kernel@lists.infradead.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: f.fainelli@gmail.com, robh+dt@kernel.org, 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
Subject: Re: [RFC 02/13] driver core: Introduce MMIO configuration
Date: Tue, 02 Mar 2021 15:09:09 +0100 [thread overview]
Message-ID: <9286657b0e4873eaaaa2208364b310d82bcc0962.camel@suse.de> (raw)
In-Reply-To: <644fd416-ab64-f1cc-ffb0-ea5649e3b600@arm.com>
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Hi Robin,
On Tue, 2021-03-02 at 11:29 +0000, Robin Murphy wrote:
> On 2021-02-26 14:02, Nicolas Saenz Julienne wrote:
> > Some devices might inadvertently sit on buses that don't support 64bit
> > MMIO access, and need a mechanism to query these limitations without
> > prejudice to other buses in the system (i.e. defaulting to 32bit access
> > system wide isn't an option).
> >
> > Introduce a new bus callback, 'mmio_configure(),' which will take care
> > of populating the relevant device properties based on the bus'
> > limitations.
>
> Devil's advocate: there already exist workarounds for 8-bit and/or
> 16-bit accesses not working in various places, does it make sense for a
> 64-bit workaround to be so wildly different and disjoint?
Can you point out an example of the workarounds?
> > Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
> > ---
> > arch/Kconfig | 8 ++++++++
> > drivers/base/dd.c | 6 ++++++
> > include/linux/device.h | 3 +++
> > include/linux/device/bus.h | 3 +++
> > 4 files changed, 20 insertions(+)
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 2bb30673d8e6..ba7f246b6b9d 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -1191,6 +1191,14 @@ config ARCH_SPLIT_ARG64
> > config ARCH_HAS_ELFCORE_COMPAT
> > bool
> >
> >
> > +config ARCH_HAS_64BIT_MMIO_BROKEN
> > + bool
> > + depends on 64BIT
>
> As mentioned previously, 32-bit systems may not need the overrides for
> kernel I/O accessors, but they could still need the same workarounds for
> the memory-mapping implications (if this is to be a proper generic
> mechanism).
I'll keep it in mind.
> > + default n
>
> Tip: it is always redundant to state that.
Noted!
Regards,
Nicolas
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next prev parent reply other threads:[~2021-03-03 22:15 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-26 14:02 [RFC 00/13] Generic way of dealing with broken 64-bit buses Nicolas Saenz Julienne
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 [this message]
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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