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

[Guenter Roeck]

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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