From: khalasa@piap.pl (Krzysztof Hałasa)
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Koen Vandeputte <koen.vandeputte@ncentric.com>,
linux-arm-kernel@lists.infradead.org,
Rob Herring <robh@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Tim Harvey <tharvey@gateworks.com>,
Russell King <linux@armlinux.org.uk>,
stable@vger.kernel.org, Robin Leblon <robin.leblon@ncentric.com>,
Olof Johansson <olof@lixom.net>,
linux-pci@vger.kernel.org
Subject: Re: [PATCH] arm: cns3xxx: fix writing to wrong PCI registers after alignment
Date: Mon, 31 Dec 2018 11:14:28 +0100 [thread overview]
Message-ID: <m336qegfzv.fsf@t19.piap.pl> (raw)
In-Reply-To: <20181230010625.GC159477@google.com> (Bjorn Helgaas's message of "Sat, 29 Dec 2018 19:06:26 -0600")
Hi,
Bjorn Helgaas <helgaas@kernel.org> writes:
> 802b7c06adc7 replaced cns3xxx_pci_write_config(), which always used
> __raw_writel() so it only did 32-bit accesses, with
> pci_generic_config_write(), which uses writeb/writew/writel()
> depending on the size.
>
> 802b7c06adc7 also converted cns3xxx_pci_read_config() from always
> using __raw_readl() (a 32-bit access) to using
> pci_generic_config_read32(), which also always does a 32-bit access.
>
> This makes me think the cnx3xxx hardware is only capable of 32-bit
> accesses, and this patch should change the driver to use
> pci_generic_config_write32() instead of pci_generic_config_write() in
> addition to the mapping fix above.
Hasn't it already been verified that the CNS3xxx can do 8-bit accesses
(and probably 16-bit ones as well), and that the docs don't mention any
such limitation?
> I don't think hardware that only supports 32-bit PCI writes can be
> quite spec-compliant (see the comments in
> pci_generic_config_write32()). So (1) you may see an additional
> dmesg warning when you convert to use it, and (2) it's possible that
> there may still be instability related to the corruption caused by
> using a 32-bit write when an 8-bit write was intended.
Right. I think IDE/SATA controllers are affected, for example.
--
Krzysztof Halasa
Industrial Research Institute for Automation and Measurements PIAP
Al. Jerozolimskie 202, 02-486 Warsaw, Poland
next prev parent reply other threads:[~2018-12-31 10:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20181218111743.25566-1-koen.vandeputte@ncentric.com>
2018-12-30 1:06 ` [PATCH] arm: cns3xxx: fix writing to wrong PCI registers after alignment Bjorn Helgaas
2018-12-31 10:14 ` Krzysztof Hałasa [this message]
2018-12-31 15:29 ` Bjorn Helgaas
2019-01-07 8:58 ` Koen Vandeputte
2019-01-07 13:24 ` Bjorn Helgaas
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