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From: Keith Busch <kbusch@kernel.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: Lukas Wunner <lukas@wunner.de>, linux-pci@vger.kernel.org
Subject: Re: PCI service interrupt handlers & access to PCI config space
Date: Tue, 13 Apr 2021 00:09:20 +0900	[thread overview]
Message-ID: <20210412150920.GA13470@redsun51.ssa.fujisawa.hgst.com> (raw)
In-Reply-To: <20210412140451.672makicwd6z6oln@pali>

On Mon, Apr 12, 2021 at 04:04:51PM +0200, Pali Rohár wrote:
> On Sunday 11 April 2021 20:25:55 Keith Busch wrote:
> > On Sat, Apr 10, 2021 at 06:26:22PM +0200, Lukas Wunner wrote:
> > > 
> > > 1.5 sec is definitely too long.  This sounds like a quirk of this
> > > specific hardware.  Try to find out if the hardware can be configured
> > > differently to respond quicker.
> > 
> > While 1.5 sec is long, pcie spec's device control 2 register has an option to
> > be even longer: up to 64 seconds for a config access timeout! I'm not sure of
> > the reasoning to allow something that high, but I think the operating system
> > would be not be too happy with that.
> 
> So what can we do in this case? On single core CPU it means that raw
> spin lock would completely block any operation on CPU for 64 seconds.

I don't think it would work here. I'm just saying that while 1.5s config
access is quite long, the spec provides an option where times exceeding
that are expected.

I have never seen a device configured that way, though. The completion
timeouts are usually set in milliseconds.

> Do you know what is the timeout for other registers?

The Device Control Register 2 timeout value is the setting for all
non-posted requests.

  reply	other threads:[~2021-04-12 15:09 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-10 12:28 PCI service interrupt handlers & access to PCI config space Pali Rohár
2021-04-10 14:25 ` Lukas Wunner
2021-04-10 15:17   ` Pali Rohár
2021-04-10 16:26     ` Lukas Wunner
2021-04-12  2:25       ` Keith Busch
2021-04-12 14:04         ` Pali Rohár
2021-04-12 15:09           ` Keith Busch [this message]
2021-04-13  9:33             ` Pali Rohár
2021-04-13  9:35       ` Pali Rohár

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