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

[Jayachandran C.]

On Wed, Apr 29, 2015 at 06:43:57PM +0100, Lorenzo Pieralisi wrote:
> On Wed, Apr 29, 2015 at 01:34:20PM +0100, Arnd Bergmann wrote:
> > On Wednesday 29 April 2015 17:09:58 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 at broadcom.com>
> > 
> > This seems very useful
> 
> Yes, it is getting less awful, waiting for pci_sys_data to disappear.
> 
> > > -static int gen_pci_setup(int nr, struct pci_sys_data *sys)
> > > +static int gen_pci_init(struct device *dev, struct gen_pci *pci)
> > >  {
> > > -	struct gen_pci *pci = sys->private_data;
> > > -	list_splice_init(&pci->resources, &sys->resources);
> > > -	return 1;
> > > +	struct pci_bus *bus;
> > > +
> > > +	pci_add_flags(PCI_REASSIGN_ALL_RSRC);
> > 
> > Do we want to set that flag unconditionally? At least for servers,
> > the resources should get assigned by firmware, and things might
> > go wrong if Linux tries to reassign them. This is probably the
> > case on kvmtool as well.

I can skip setting this flag if PCI_PROBE_ONLY is set. Adding another
device tree parameter for this may not be needed.

> I will give it a go on kvmtool, but at first glance concern is
> shared.
> 
> > > +	bus = pci_scan_root_bus(dev, 0, &gen_pci_ops, pci, &pci->resources);
> > > +	if (!bus) {
> > > +		dev_err(dev, "Scanning rootbus failed");
> > > +		return -ENODEV;
> > > +	}
> > > +	pci_fixup_irqs(pci_common_swizzle, of_irq_parse_and_map_pci);
> > 
> > I thought this was done by default now. If it is not, can
> > we make the of_irq swizzling the default?
> 
> Possibly yes.

I am not sure I understand this, I thought pci_fixup_irqs needs to be
called at this point.

> > > +	if (!pci_has_flag(PCI_PROBE_ONLY)) {
> > > +		pci_bus_size_bridges(bus);
> > > +		pci_bus_assign_resources(bus);
> > > +	}
> > > +	pci_bus_add_devices(bus);
> > > +
> > > +	/* Configure PCI Express settings */
> > > +	if (pci_has_flag(PCI_PROBE_ONLY)) {
> > > +		struct pci_bus *child;
> > > +
> > > +		list_for_each_entry(child, &bus->children, node)
> > > +			pcie_bus_configure_settings(child);
> > > +	}
> > > +	return 0;
> > >  }
> > 
> > We should also try to come up wtih a way to make that
> > pcie_bus_configure_settings() automatic if it's required here.
> > 
> > >  static int gen_pci_probe(struct platform_device *pdev)
> > > @@ -214,13 +237,6 @@ static int gen_pci_probe(struct platform_device *pdev)
> > >  	struct device *dev = &pdev->dev;
> > >  	struct device_node *np = dev->of_node;
> > >  	struct gen_pci *pci = devm_kzalloc(dev, sizeof(*pci), GFP_KERNEL);
> > > -	struct hw_pci hw = {
> > > -		.nr_controllers	= 1,
> > > -		.private_data	= (void **)&pci,
> > > -		.setup		= gen_pci_setup,
> > > -		.map_irq	= of_irq_parse_and_map_pci,
> > > -		.ops		= &gen_pci_ops,
> > > -	};
> > >  
> > >  	if (!pci)
> > >  		return -ENOMEM;
> > > @@ -258,8 +274,7 @@ static int gen_pci_probe(struct platform_device *pdev)
> > >  		return err;
> > >  	}
> > >  
> > > -	pci_common_init_dev(dev, &hw);
> > > -	return 0;
> > > +	return gen_pci_init(dev, pci);
> > 
> > How about moving the new code right into the probe() function?
> 
> +1.

I will add this to patch v2.
 
> I suspect the PCI_PROBE_ONLY case was not tested on arm64, since we
> still need a patch to prevent resources enablement there (in the
> pcibios_enable_device call - actually the check for PCI_PROBE_ONLY
> should be moved to the default pcibios_enable_device function in
> drivers/pci/pci.c).
> 
> The other bit missing is MSI handling, that should still be implemented.

I think we should parse msi-parent and set ->msi on the root bus in
pci-host-generic.c. The implementation of pcibios_msi_controller() for
arm/arm64 can go up the bus hierarchy and return the first msi
controller it finds. This would be trivial to add to arm/arm64.
I can post a follow up patch for this if you are interested.

If there are no additional concerns, I can post v2 of the patch after
testing on arm.

Thanks,
JC.