linux-kernel - Re: Purpose of pci_remap

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Date:	Wed, 13 Jul 2016 17:13:03 +0100
From:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:	Bharat Kumar Gogada <bharat.kumar.gogada@...inx.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Liviu.Dudau@....com" <Liviu.Dudau@....com>,
	nofooter <nofooter@...inx.com>,
	"thomas.petazzoni@...e-electrons.com" 
	<thomas.petazzoni@...e-electrons.com>
Subject: Re: Purpose of pci_remap_iospace

On Wed, Jul 13, 2016 at 03:16:21PM +0000, Bharat Kumar Gogada wrote:
> > Subject: Re: Purpose of pci_remap_iospace
> >
> > On Wednesday, July 13, 2016 12:30:44 PM CEST Bharat Kumar Gogada wrote:
> > >  > On Wednesday, July 13, 2016 8:11:56 AM CEST Bharat Kumar Gogada
> > wrote:
> > > > > > Subject: Re: Purpose of pci_remap_iospace
> > > >
> > > > I notice you have 1MB of I/O space here
> > > >
> > > > > Kernel Boot log:
> > > > > [    2.345294] nwl-pcie fd0e0000.pcie: Link is UP
> > > > > [    2.345339] PCI host bridge /amba/pcie@...e0000 ranges:
> > > > > [    2.345356]   No bus range found for /amba/pcie@...e0000, using
> > [bus
> > > > 00-ff]
> > > > > [    2.345382]    IO 0xe0000000..0xe00fffff -> 0x00000000
> > > > > [    2.345401]   MEM 0xe0100000..0xeeffffff -> 0xe0100000
> > > > > [    2.345498] nwl-pcie fd0e0000.pcie: PCI host bridge to bus 0000:00
> > > > > [    2.345517] pci_bus 0000:00: root bus resource [bus 00-ff]
> > > > > [    2.345533] pci_bus 0000:00: root bus resource [io  0x0000-0xfffff]
> > > >
> > > > and all of it gets mapped by the PCI core. Usually you only have 64K
> > > > of I/O space per host bridge, and the PCI core should perhaps not
> > > > try to map all of it, though I don't think this is actually your problem here.
> > > >
> > > > > [    2.345550] pci_bus 0000:00: root bus resource [mem 0xe0100000-
> > > > 0xeeffffff]
> > > > > [    2.345770] pci 0000:00:00.0: cannot attach to SMMU, is it on the same
> > > > bus?
> > > > > [    2.345786] iommu: Adding device 0000:00:00.0 to group 1
> > > > > [    2.346142] pci 0000:01:00.0: cannot attach to SMMU, is it on the same
> > > > bus?
> > > > > [    2.346158] iommu: Adding device 0000:01:00.0 to group 1
> > > > > [    2.346213] pci 0000:00:00.0: BAR 8: assigned [mem 0xe0100000-
> > > > 0xe02fffff]
> > > > > [    2.346234] pci 0000:01:00.0: BAR 0: assigned [mem 0xe0100000-
> > 0xe01fffff
> > > > 64bit]
> > > > > [    2.346268] pci 0000:01:00.0: BAR 2: assigned [mem 0xe0200000-
> > 0xe02fffff
> > > > 64bit]
> > > > > [    2.346300] pci 0000:01:00.0: BAR 4: no space for [io  size 0x0040]
> > > > > [    2.346316] pci 0000:01:00.0: BAR 4: failed to assign [io  size 0x0040]
> > > > > [    2.346333] pci 0000:00:00.0: PCI bridge to [bus 01-0c]
> > > > > [    2.346350] pci 0000:00:00.0:   bridge window [mem 0xe0100000-
> > > > 0xe02fffff]
> > > > >
> > > > > IO assignment fails.
> > > >
> > > > I would guess that the I/O space is not registered correctly. Is
> > > > this drivers/pci/host/pcie-xilinx.c ? We have had problems with this
> > > > in the past, since almost nobody uses I/O space and it requires
> > > > several steps to all be done correctly.
> > > >
> > > Thanks Arnd.
> > >
> > > we are testing using drivers/pci/host/pcie-xilinx-nwl.c.
> >
> > According to Documentation/devicetree/bindings/pci/xilinx-nwl-pcie.txt,
> > this hardware does not support I/O space.
> 
> We received a newer IP version with IO support, so we are trying to test this feature.
> >
> > Is this on ARM or microblaze?
> 
> It is ARM 64-bit.
> 
> > This has neither the PCI memory nor the I/O resource, it looks like you never
> > call pci_add_resource_offset() to start with, or maybe it fails for some
> > reason.
> 
> I see that above API is used in ARM drivers, do we need to do it in
> ARM64 also ?

It is called in of_pci_get_host_bridge_resources(), since you
are using that API there is nothing more you have to do. The problem
with resources in /proc/iomem and /proc/ioports is that you
do not request the host bridge apertures in your host controller
driver, see drivers/pci/host/pci-host-common.c (devm_request_resource())
to see how to do it.

And as I said previously in this thread none of this is related to
your IO BAR assignment failures IMHO.

Lorenzo