Linux-ARM-Kernel Archive on lore.kernel.org
 help / color / Atom feed
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
Message-ID: <9286657b0e4873eaaaa2208364b310d82bcc0962.camel@suse.de> (raw)
In-Reply-To: <644fd416-ab64-f1cc-ffb0-ea5649e3b600@arm.com>

[-- Attachment #1.1: Type: text/plain, Size: 1835 bytes --]

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


[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 488 bytes --]

[-- Attachment #2: Type: text/plain, Size: 176 bytes --]

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply index

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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=9286657b0e4873eaaaa2208364b310d82bcc0962.camel@suse.de \
    --to=nsaenzjulienne@suse.de \
    --cc=ardb@kernel.org \
    --cc=arnd@arndb.de \
    --cc=catalin.marinas@arm.com \
    --cc=devicetree@vger.kernel.org \
    --cc=dwmw2@infradead.org \
    --cc=f.fainelli@gmail.com \
    --cc=hch@infradead.org \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux@armlinux.org.uk \
    --cc=narmstrong@baylibre.com \
    --cc=robh+dt@kernel.org \
    --cc=robin.murphy@arm.com \
    --cc=will@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-ARM-Kernel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/0 linux-arm-kernel/git/0.git
	git clone --mirror https://lore.kernel.org/linux-arm-kernel/1 linux-arm-kernel/git/1.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-arm-kernel linux-arm-kernel/ https://lore.kernel.org/linux-arm-kernel \
		linux-arm-kernel@lists.infradead.org
	public-inbox-index linux-arm-kernel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-arm-kernel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git