From: Alexander Sverdlin <alexander.sverdlin@nokia.com>
To: ext Jiri Kosina <jkosina@suse.cz>
Cc: Ralf Baechle <ralf@linux-mips.org>,
linux-mips@linux-mips.org, David Daney <ddaney@cavium.com>,
ddaney.cavm@gmail.com, "ext Daney,
David" <David.Daney@caviumnetworks.com>,
Rob Herring <robh@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>,
Masanari Iida <standby24x7@gmail.com>,
Bjorn Helgaas <bhelgaas@google.com>,
"Rulf, Mathias (Nokia - DE/Ulm)" <mathias.rulf@nokia.com>
Subject: Re: [PATCH] pci: octeon: Remove udelay() causing huge IRQ latency
Date: Wed, 18 Mar 2015 15:15:14 +0100 [thread overview]
Message-ID: <55098872.9010605@nokia.com> (raw)
In-Reply-To: <alpine.LNX.2.00.1503181409110.6781@pobox.suse.cz>
Hi!
On 18/03/15 14:11, ext Jiri Kosina wrote:
>> udelay() in PCI/PCIe read/write callbacks cause 30ms IRQ latency on Octeon
>> > platforms because these operations are called from PCI_OP_READ() and
>> > PCI_OP_WRITE() under raw_spin_lock_irqsave().
>> >
>> > Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
> I have no idea about the octeon platform, but how do you deal with the
> fact that is stated by the comment you are removing? I.e.
>
> /* Some PCI cards require delays when accessing config space. */
>
> Is that not the case any more for some reason? If not, it really needs to
> be explained in the changelog.
This udelay() should not have made its way upstream, someone overseen it during
code review. This is simply not allowed to have delayed read/write in the current
Linux PCI subsystem. And maybe there is no place for it at all.
--
Best regards,
Alexander Sverdlin.
next prev parent reply other threads:[~2015-03-18 14:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-18 13:05 [PATCH] pci: octeon: Remove udelay() causing huge IRQ latency Alexander Sverdlin
2015-03-18 13:11 ` Jiri Kosina
2015-03-18 14:15 ` Alexander Sverdlin [this message]
2015-03-18 16:11 ` David Daney
2015-03-18 16:11 ` David Daney
2015-03-18 16:17 ` Alexander Sverdlin
2015-03-18 18:06 ` Aaro Koskinen
2015-03-19 14:55 ` Alexander Sverdlin
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