Re: [PATCH v4 5/5] PCI: Handle Enhanced Allocation (EA) capability for bridges

[David Daney]

On 10/05/2015 03:54 PM, Sean O. Stalley wrote:
> On Fri, Oct 02, 2015 at 03:37:56PM -0700, David Daney wrote:
> > From: David Daney <david.daney@xxxxxxxxxx>
> >
> > PCI bridges may have their properties be specified via EA entries.
> >
> > Extend the EA parser to extract the bridge resources, and modify
> > pci_read_bridge_{io,mmio,mmio_pref}() to use resources previously
> > obtained via EA.
> >
> > Save the offset to the EA capability in struct pci_dev, and use it to
> > easily find the EA bridge subordinate and secondary bus numbers.
> >
> > When assigning the bridge resources a couple of changes are required
> > so that the EA obtained IORESOURCE_PCI_FIXED are not resized, and
> > correctly linked into the resource tree.
> >
> > 1) In pbus_size_mem() do not attempt to resize the bridge resources if
> >     they are marked as IORESOURCE_PCI_FIXED.
> >
> > 2) In pci_bus_alloc_from_region()for IORESOURCE_PCI_FIXED resources, just
> >     try to request the resource as is, without attempting to resize it.
> >
> > Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
> > ---
> >   drivers/pci/bus.c       |  7 +++++++
> >   drivers/pci/pci.c       | 13 +++++++++++++
> >   drivers/pci/probe.c     | 31 +++++++++++++++++++++++++++++--
> >   drivers/pci/setup-bus.c |  3 +++
> >   include/linux/pci.h     |  1 +
> >   5 files changed, 53 insertions(+), 2 deletions(-)
> > @@ -801,8 +813,23 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
> >
> >   	pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);
> >   	primary = buses & 0xFF;
> > -	secondary = (buses >> 8) & 0xFF;
> > -	subordinate = (buses >> 16) & 0xFF;
> > +	if (dev->ea_cap) {
> > +		u32 dw1;
> > +
> > +		pci_read_config_dword(dev, dev->ea_cap + 4, &dw1);
> > +		if (dw1 & 0xFF)
> > +			secondary = dw1 & 0xFF;
> > +		else
> > +			secondary = (buses >> 8) & 0xFF;
> > +
> > +		if ((dw1 >> 8) & 0xFF)
> > +			subordinate = (dw1 >> 8) & 0xFF;
> > +		else
> > +			subordinate = (buses >> 16) & 0xFF;
> > +	} else {
> > +		secondary = (buses >> 8) & 0xFF;
> > +		subordinate = (buses >> 16) & 0xFF;
> > +	}
>
> We can refactor this to make it cleaner/more compact. from V3 review:
>
>
> 	secondary = (buses >> 8) & 0xFF;
> 	subordinate = (buses >> 16) & 0xFF;
> 	if (dev->ea_cap) {
> 		u32 sdw;
> 		
> 		pci_read_config_dword(dev, dev->ea_cap + 4, &sdw);
> 		
> 		if (sdw & 0xFF)
> 			secondary = sdw & 0xFF;
> 		
> 		sdw >>= 8;
> 		if (sdw & 0xFF)
> 			subordinate = sdw & 0xFF;
> 	}

Yes, that is cleaner.  I think I didn't read the comments on v3 closely 
enough.  I will switch to doing it this way.

Thanks,
David Daney


> -Sean
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