From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: "Pali Rohár" <pali@kernel.org>
Cc: "Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
"Andrew Murray" <amurray@thegoodpenguin.co.uk>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Marek Behún" <marek.behun@nic.cz>,
"Remi Pommarel" <repk@triplefau.lt>,
"Tomasz Maciej Nowak" <tmn505@gmail.com>,
Xogium <contact@xogium.me>,
linux-pci@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] PCI: aardvark: Don't touch PCIe registers if no card connected
Date: Fri, 10 Jul 2020 10:18:00 +0100 [thread overview]
Message-ID: <20200710091800.GA3419@e121166-lin.cambridge.arm.com> (raw)
In-Reply-To: <20200709150959.wq6zfkcy4m6hvvpl@pali>
On Thu, Jul 09, 2020 at 05:09:59PM +0200, Pali Rohár wrote:
[...]
> > I understand that but the bridge bus resource can be trimmed to just
> > contain the root bus because that's the only one where there is a
> > chance you can enumerate a device.
>
> It is possible to register only root bridge without endpoint?
It is possible to register the root bridge with a trimmed IORESOURCE_BUS
so that you don't enumerate anything other than the root port.
> > I would like to get Bjorn's opinion on this, I don't like these "link is
> > up" checks in config accessors (they are racy and honestly it is a
> > run-time check that does not make much sense, either it is always
> > true/false or it is inevitably racy)
>
> It is runtime check, but does not have to be always true/false. I have
> tested more Compex wifi cards and under certain conditions they
> "disappear" from the bus during usage.
I would be very grateful if you could describe what happens in HW
when these conditions trigger - I would like to understand if this
issue is aardvark specific or it isn't.
> So I think it still make sense to do this "fast" check as it is only
> optimization.
I will merge this patch but I'd also like to understand the underlying
issue better.
Thanks,
Lorenzo
WARNING: multiple messages have this Message-ID (diff)
From: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To: "Pali Rohár" <pali@kernel.org>
Cc: "Tomasz Maciej Nowak" <tmn505@gmail.com>,
linux-pci@vger.kernel.org, Xogium <contact@xogium.me>,
linux-kernel@vger.kernel.org, "Marek Behún" <marek.behun@nic.cz>,
"Remi Pommarel" <repk@triplefau.lt>,
"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
"Bjorn Helgaas" <bhelgaas@google.com>,
linux-arm-kernel@lists.infradead.org,
"Andrew Murray" <amurray@thegoodpenguin.co.uk>
Subject: Re: [PATCH v3] PCI: aardvark: Don't touch PCIe registers if no card connected
Date: Fri, 10 Jul 2020 10:18:00 +0100 [thread overview]
Message-ID: <20200710091800.GA3419@e121166-lin.cambridge.arm.com> (raw)
In-Reply-To: <20200709150959.wq6zfkcy4m6hvvpl@pali>
On Thu, Jul 09, 2020 at 05:09:59PM +0200, Pali Rohár wrote:
[...]
> > I understand that but the bridge bus resource can be trimmed to just
> > contain the root bus because that's the only one where there is a
> > chance you can enumerate a device.
>
> It is possible to register only root bridge without endpoint?
It is possible to register the root bridge with a trimmed IORESOURCE_BUS
so that you don't enumerate anything other than the root port.
> > I would like to get Bjorn's opinion on this, I don't like these "link is
> > up" checks in config accessors (they are racy and honestly it is a
> > run-time check that does not make much sense, either it is always
> > true/false or it is inevitably racy)
>
> It is runtime check, but does not have to be always true/false. I have
> tested more Compex wifi cards and under certain conditions they
> "disappear" from the bus during usage.
I would be very grateful if you could describe what happens in HW
when these conditions trigger - I would like to understand if this
issue is aardvark specific or it isn't.
> So I think it still make sense to do this "fast" check as it is only
> optimization.
I will merge this patch but I'd also like to understand the underlying
issue better.
Thanks,
Lorenzo
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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-07-10 9:18 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-28 14:31 [PATCH] PCI: aardvark: Don't touch PCIe registers if no card connected Pali Rohár
2020-05-28 14:31 ` Pali Rohár
2020-05-28 16:26 ` Bjorn Helgaas
2020-05-28 16:26 ` Bjorn Helgaas
2020-05-28 16:38 ` Pali Rohár
2020-05-28 16:38 ` Pali Rohár
2020-05-28 16:49 ` Bjorn Helgaas
2020-05-28 16:49 ` Bjorn Helgaas
2020-05-29 8:30 ` Pali Rohár
2020-05-29 8:30 ` Pali Rohár
2020-06-30 12:31 ` Pali Rohár
2020-06-30 12:31 ` Pali Rohár
2020-06-30 13:51 ` Bjorn Helgaas
2020-06-30 13:51 ` Bjorn Helgaas
2020-06-30 14:04 ` Pali Rohár
2020-06-30 14:04 ` Pali Rohár
2020-06-30 14:58 ` Bjorn Helgaas
2020-06-30 14:58 ` Bjorn Helgaas
2020-07-01 8:08 ` Pali Rohár
2020-07-01 8:08 ` Pali Rohár
2020-07-01 8:20 ` [PATCH v2] " Pali Rohár
2020-07-01 8:20 ` Pali Rohár
2020-07-01 21:34 ` Bjorn Helgaas
2020-07-01 21:34 ` Bjorn Helgaas
2020-07-02 8:23 ` Pali Rohár
2020-07-02 8:23 ` Pali Rohár
2020-07-02 8:30 ` [PATCH v3] " Pali Rohár
2020-07-02 8:30 ` Pali Rohár
2020-07-09 11:35 ` Lorenzo Pieralisi
2020-07-09 11:35 ` Lorenzo Pieralisi
2020-07-09 12:22 ` Pali Rohár
2020-07-09 12:22 ` Pali Rohár
2020-07-09 14:47 ` Lorenzo Pieralisi
2020-07-09 14:47 ` Lorenzo Pieralisi
2020-07-09 15:09 ` Pali Rohár
2020-07-09 15:09 ` Pali Rohár
2020-07-10 9:18 ` Lorenzo Pieralisi [this message]
2020-07-10 9:18 ` Lorenzo Pieralisi
2020-07-10 15:44 ` Pali Rohár
2020-07-10 15:44 ` Pali Rohár
2020-07-10 16:08 ` Bjorn Helgaas
2020-07-10 16:08 ` Bjorn Helgaas
2020-07-10 19:30 ` Pali Rohár
2020-07-10 19:30 ` Pali Rohár
2020-07-10 20:08 ` Bjorn Helgaas
2020-07-10 20:08 ` Bjorn Helgaas
2020-07-13 8:27 ` Pali Rohár
2020-07-13 8:27 ` Pali Rohár
2020-07-13 11:23 ` Lorenzo Pieralisi
2020-07-13 11:23 ` Lorenzo Pieralisi
2020-07-13 14:50 ` Pali Rohár
2020-07-13 14:50 ` Pali Rohár
2020-07-13 16:41 ` Lorenzo Pieralisi
2020-07-13 16:41 ` Lorenzo Pieralisi
2020-07-14 7:38 ` Pali Rohár
2020-07-14 7:38 ` Pali Rohár
2020-07-15 12:17 ` Pali Rohár
2020-07-15 12:17 ` Pali Rohár
2020-07-15 16:21 ` Lorenzo Pieralisi
2020-07-15 16:21 ` Lorenzo Pieralisi
2020-07-21 8:57 ` Pali Rohár
2020-07-21 8:57 ` Pali Rohár
2020-07-21 10:48 ` Lorenzo Pieralisi
2020-07-21 10:48 ` Lorenzo Pieralisi
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