Re: [PATCH v2 1/2] PCI: generic: remove dependency on hw_pci

[Will Deacon <will.deacon@arm.com>]

On Wed, May 20, 2015 at 12:09:18AM +0100, Bjorn Helgaas wrote:
> On Tue, May 12, 2015 at 05:37:47AM +0530, Jayachandran C. wrote:
> > On Tue, May 05, 2015 at 04:53:46PM +0100, Will Deacon wrote:
> > > On Tue, May 05, 2015 at 03:02:12AM +0100, Jayachandran C wrote:
> > > > The current code in pci-host-generic.c uses pci_common_init_dev()
> > > > from the arch/arm/ to do a part of the PCI initialization, and this
> > > > prevents it from being used on arm64.
> > > > 
> > > > The initialization done by pci_common_init_dev() that is really
> > > > needed by pci-host-generic.c can be done in the same file without
> > > > using the hw_pci API of ARM.
> > > > 
> > > > The ARM platform requires a pci_sys_data as sysdata for the PCI bus,
> > > > this is be handled by setting up 'struct gen_pci' to embed a
> > > > pci_sys_data variable as the first element on the ARM platform.
> > > > 
> > > > Signed-off-by: Jayachandran C <jchandra@broadcom.com>
> > > > ---
> > > > Here's v2 of the patches, this enables use of pci-host-generic on
> > > > arm64.
> > > > 
> > > > This has been tested on both qemu and fast model for arm64, and on
> > > > qemu for arm32.
> > > > 
> > > > v1->v2
> > > >  - Address comments from Arnd Bergmann and Lorenzo Pieralisi
> > > >     - move contents of gen_pci_init to gen_pci_probe
> > > >     - assign resources only when !probe_only
> > > >  - tested on ARM32 with qemu option -M virt
> > > 
> > > I tried this with an arm64 kernel running under kvmtool, but I get the
> > > following errors (a 32-bit ARM kernel does seem to work):
> > > 
> > >   PCI host bridge /pci ranges:
> > >      IO 0x00000000..0x0000ffff -> 0x00000000
> > >     MEM 0x41000000..0x7fffffff -> 0x41000000
> > >   pci-host-generic 40000000.pci: PCI host bridge to bus 0000:00
> > >   pci_bus 0000:00: root bus resource [bus 00-01]
> > >   pci_bus 0000:00: root bus resource [io  0x0000-0xffff]
> > >   pci_bus 0000:00: root bus resource [mem 0x41000000-0x7fffffff]
> > >   pci_bus 0000:00: scanning bus
> > >   pci 0000:00:00.0: [1af4:1009] type 00 class 0xff0000
> > >   pci 0000:00:00.0: reg 0x10: [mem 0x41000000-0x410003ff]
> > >   pci 0000:00:00.0: reg 0x14: [io  0x6200-0x65ff]
> > >   pci 0000:00:00.0: reg 0x18: [mem 0x41000400-0x410005ff]
> > >   pci 0000:00:01.0: [1af4:1009] type 00 class 0xff0000
> > >   pci 0000:00:01.0: reg 0x10: [mem 0x41000800-0x41000bff]
> > >   pci 0000:00:01.0: reg 0x14: [io  0x6600-0x69ff]
> > >   pci 0000:00:01.0: reg 0x18: [mem 0x41000c00-0x41000dff]
> > >   pci_bus 0000:00: fixups for bus
> > >   pci_bus 0000:00: bus scan returning with max=00
> > >   pci 0000:00:00.0: fixup irq: got 10
> > >   pci 0000:00:00.0: assigning IRQ 10
> > >   pci 0000:00:01.0: fixup irq: got 11
> > >   pci 0000:00:01.0: assigning IRQ 11
> > >   virtio-pci 0000:00:00.0: can't enable device: BAR 0 [mem 0x41000000-0x410003ff] not claimed
> > >   virtio-pci: probe of 0000:00:00.0 failed with error -22
> > >   virtio-pci 0000:00:01.0: can't enable device: BAR 0 [mem 0x41000800-0x41000bff] not claimed
> > >   virtio-pci: probe of 0000:00:01.0 failed with error -22
> > 
> > PCI_PROBE_ONLY does not work yet for arm64, this will need further changes
> > in either arm64 or pci as noted by Lorenzo. This is not due to a problem with
> > this patch per se.
> > 
> > More importantly, this does not change the current arm32 behavior and adds
> > support for arm64 for two very useful cases
> >  - we can use "pci-host-ecam-generic" for a host bridge controller that is
> >    initialized by firmware, without adding a custom driver.
> >  - qemu virt platform works on arm64
> > 
> > If you think there are any furhter changes needed in this patchset please
> > let me know.
> 
> I'm waiting for at least an ack from Will.

I'm not too keen on the current state of this patch. Firstly, I'd really
like to see the PROBE_ONLY case addressed at the same time as this port
(Lorenzo and Suravee are working on this). Secondly, the hack to put
pci_sys_data as the first member of gen_pci is ugly at best and probably
makes it difficult to support MSIs on ARM.

Will