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

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

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@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 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.

> > +	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 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.

Lorenzo