Re: [RFC/RFT PATCH v2] PCI: move pci_read_bridge_bases to the generic PCI layer

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On 06/09/2015 02:01 AM, Lorenzo Pieralisi wrote:
When a PCI bus is scanned, upon PCI bridge detection the kernel
has to read the bridge registers to set-up its resources so that
the PCI resource hierarchy can be validated properly.

Most if not all architectures read PCI bridge registers in the
pcibios_fixup_bus hook, that is called by the PCI generic layer
whenever a PCI bus is scanned.

Since pci_read_bridge_bases is an arch agnostic operation (and it
is carried out on all architectures) it can be moved to the generic
PCI layer in order to consolidate code and remove the respective
calls from the architectures back-ends.

The PCI_PROBE_ONLY flag is not checked before calling
pci_read_bridge_buses in the generic layer since reading the bridge
bases is not related to resources assignment; this implies that it
can be carried out safely on PCI_PROBE_ONLY systems too and should
not affect architectures (alpha, mips) that check the PCI_PROBE_ONLY
flag before reading the bridge bases.

In order to validate the resource hierarchy as soon as the resources
themselves are probed (ie read from the bridge), this patch also adds
code to pci_read_bridge_bases that claims the bridge resources, so that
they are validated and inserted in the resource hierarchy as soon as
the bridge bases are probed.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: James E.J. Bottomley <jejb@xxxxxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Cc: Michal Simek <monstr@xxxxxxxxx>
Cc: Chris Zankel <chris@xxxxxxxxxx>

Working fine on powerpc (tested with Freescale P2020 and P5020) as well as x86
(tested on two different server class systems).

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Guenter

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