From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Bjorn Helgaas <helgaas@kernel.org>, Arnd Bergmann <arnd@arndb.de>
Cc: "Saheed O. Bolarinwa" <refactormyself@gmail.com>,
bjorn@helgaas.com, Shuah Khan <skhan@linuxfoundation.org>,
linux-pci <linux-pci@vger.kernel.org>,
linux-kernel-mentees@lists.linuxfoundation.org,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Richard Henderson <rth@twiddle.net>,
Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
Matt Turner <mattst88@gmail.com>,
Greg Ungerer <gerg@linux-m68k.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
Russell King <linux@armlinux.org.uk>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@samba.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
"David S. Miller" <davem@davemloft.net>,
sparclinux <sparclinux@vger.kernel.org>,
Guenter Roeck <linux@roeck-us.net>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Heiner Kallweit <hkallweit1@gmail.com>,
Jakub Kicinski <kuba@kernel.org>, Keith Busch <kbusch@kernel.org>,
Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>,
Sagi Grimberg <sagi@grimberg.me>,
Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
Rob Herring <robh@kernel.org>,
Bjorn Helgaas <bhelgaas@google.com>,
Kevin Hilman <khilman@baylibre.com>,
Philipp Zabel <p.zabel@pengutronix.de>,
Jingoo Han <jingoohan1@gmail.com>,
Gustavo Pimentel <gustavo.pimentel@synopsys.com>,
Toan Le <toan@os.amperecomputing.com>,
Ray Jui <rjui@broadcom.com>,
Scott Branden <sbranden@broadcom.com>,
Ley Foon Tan <ley.foon.tan@intel.com>,
Marek Vasut <marek.vasut+renesas@gmail.com>,
Kjetil Oftedal <oftedal@gmail.com>
Subject: Re: [RFC PATCH 00/35] Move all PCIBIOS* definitions into arch/x86
Date: Wed, 15 Jul 2020 12:19:46 +1000 [thread overview]
Message-ID: <2629240c07af7fec5989127ed6da405e12cf77a3.camel@kernel.crashing.org> (raw)
In-Reply-To: <20200714234625.GA428442@bjorn-Precision-5520>
On Tue, 2020-07-14 at 18:46 -0500, Bjorn Helgaas wrote:
> Yes. I have no problem with that. There are a few cases where it's
> important to check for errors, e.g., we read a status register and do
> something based on a bit being set. A failure will return all bits
> set, and we may do the wrong thing. But most of the errors we care
> about will be on MMIO reads, not config reads, so we can probably
> ignore most config read errors.
And in both cases, we don't have the plumbing to provide accurate
and reliable error returns for all platforms anyways (esp. not for
MMIO).
I think it makes sense to stick to the good old "if all 1's, then go
out of line" including for config space.
../..
> Yep, except for things like device removal or other PCI errors.
A whole bunch of these are reported asynchronously, esp for writes (and
yes, including config writes, they are supposed to be non-posted but
more often than not, the path from the CPU to the PCI bridge remains
posted for writes including config ones).
> So maybe a good place to start is by removing some of the useless
> error checking for pci_read_config_*() and pci_write_config_*().
> That's a decent-sized but not impractical project that could be done
> per subsystem or something:
>
> git grep -E "(if|return|=).*\<pci_(read|write)_config" drivers
>
> finds about 400 matches.
>
> Some of those callers probably really *do* want to check for errors,
> and I guess we'd have to identify them and do them separately as you
> mentioned.
I'd be curious about these considering how unreliable our error return
is accross the board.
Cheers,
Ben.
next prev parent reply other threads:[~2020-07-15 2:22 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAK8P3a3NWSZw6678k1O2eJ6-c5GuW7484PRvEzU9MEPPrCD-yw@mail.gmail.com>
2020-07-14 18:45 ` [RFC PATCH 00/35] Move all PCIBIOS* definitions into arch/x86 Bjorn Helgaas
2020-07-14 21:02 ` Kjetil Oftedal
2020-07-15 2:14 ` Benjamin Herrenschmidt
2020-07-14 22:01 ` Arnd Bergmann
2020-07-14 23:46 ` Bjorn Helgaas
2020-07-15 2:19 ` Benjamin Herrenschmidt [this message]
2020-07-15 6:47 ` Arnd Bergmann
2020-07-15 22:26 ` Benjamin Herrenschmidt
2020-07-15 4:18 ` Oliver O'Halloran
2020-07-15 14:38 ` David Laight
2020-07-15 22:12 ` Bjorn Helgaas
2020-07-15 22:49 ` Benjamin Herrenschmidt
2020-07-16 8:07 ` David Laight
2020-07-14 23:14 ` Rob Herring
2020-07-15 2:12 ` Benjamin Herrenschmidt
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