From: Marek Behun <email@example.com>
To: "Pali Rohár" <firstname.lastname@example.org>
Cc: Rob Herring <email@example.com>, Andrew Lunn <firstname.lastname@example.org>,
Gregory Clement <email@example.com>,
Sebastian Hesselbarth <firstname.lastname@example.org>,
Subject: Re: [PATCH] arm64: dts: marvell: armada-37xx: Set linux,pci-domain to zero
Date: Thu, 15 Apr 2021 10:45:37 +0200 [thread overview]
Message-ID: <20210415104537.403de52e@thinkpad> (raw)
On Thu, 15 Apr 2021 10:36:40 +0200
Pali Rohár <email@example.com> wrote:
> On Tuesday 13 April 2021 13:17:29 Rob Herring wrote:
> > On Mon, Apr 12, 2021 at 7:41 AM Pali Rohár <firstname.lastname@example.org> wrote:
> > >
> > > Since commit 526a76991b7b ("PCI: aardvark: Implement driver 'remove'
> > > function and allow to build it as module") PCIe controller driver for
> > > Armada 37xx can be dynamically loaded and unloaded at runtime. Also driver
> > > allows dynamic binding and unbinding of PCIe controller device.
> > >
> > > Kernel PCI subsystem assigns by default dynamically allocated PCI domain
> > > number (starting from zero) for this PCIe controller every time when device
> > > is bound. So PCI domain changes after every unbind / bind operation.
> > PCI host bridges as a module are relatively new, so seems likely a bug to me.
> Why a bug? It is there since 5.10 and it is working.
> > > Alternative way for assigning PCI domain number is to use static allocated
> > > numbers defined in Device Tree. This option has requirement that every PCI
> > > controller in system must have defined PCI bus number in Device Tree.
> > That seems entirely pointless from a DT point of view with a single PCI bridge.
> If domain id is not specified in DT then kernel uses counter and assigns
> counter++. So it is not pointless if we want to have stable domain id.
What Rob is trying to say is that
- the bug is that kernel assigns counter++
- device-tree should not be used to fix problems with how kernel does
- if a device has only one PCIe controller, it is pointless to define
it's pci-domain. If there were multiple controllers, then it would
make sense, but there is only one
next prev parent reply other threads:[~2021-04-15 8:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-12 12:39 [PATCH] arm64: dts: marvell: armada-37xx: Set linux,pci-domain to zero Pali Rohár
2021-04-13 18:17 ` Rob Herring
2021-04-15 8:36 ` Pali Rohár
2021-04-15 8:45 ` Marek Behun [this message]
2021-04-15 15:13 ` Rob Herring
2021-04-17 14:49 ` Pali Rohár
2021-04-17 15:19 ` Andrew Lunn
2021-04-17 19:42 ` Pali Rohár
2021-04-23 15:33 ` Rob Herring
2021-04-25 15:21 ` Pali Rohár
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