Messages in this thread | | | Date | Wed, 27 May 2015 11:42:52 -0500 | From | Suravee Suthikulanit <> | Subject | Re: [RFC/RFT PATCH] PCI: move pci_read_bridge_bases to the generic PCI layer |
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Hi Lorenzo,
Sorry for late reply.
On 5/21/2015 8:14 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. > > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> > Cc: Ralf Baechle <ralf@linux-mips.org> > Cc: James E.J. Bottomley <jejb@parisc-linux.org> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Bjorn Helgaas <bhelgaas@google.com> > Cc: Richard Henderson <rth@twiddle.net> > Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> > Cc: David Howells <dhowells@redhat.com> > Cc: Russell King <linux@arm.linux.org.uk> > Cc: Tony Luck <tony.luck@intel.com> > Cc: David S. Miller <davem@davemloft.net> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Michal Simek <monstr@monstr.eu> > Cc: Koichi Yasutake <yasutake.koichi@jp.panasonic.com> > Cc: Chris Zankel <chris@zankel.net> > --- > arch/alpha/kernel/pci.c | 7 +------ > arch/frv/mb93090-mb00/pci-vdk.c | 2 -- > arch/ia64/pci/pci.c | 1 - > arch/microblaze/pci/pci-common.c | 9 +-------- > arch/mips/pci/pci.c | 6 ------ > arch/mn10300/unit-asb2305/pci.c | 1 - > arch/powerpc/kernel/pci-common.c | 8 +------- > arch/x86/pci/common.c | 1 - > arch/xtensa/kernel/pci.c | 4 ---- > drivers/parisc/dino.c | 3 --- > drivers/parisc/lba_pci.c | 1 - > drivers/pci/probe.c | 11 ++++++++++- > 12 files changed, 13 insertions(+), 41 deletions(-) > > [.....] > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index 062fee6..335d9f2 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -453,7 +453,11 @@ void pci_read_bridge_bases(struct pci_bus *child) > struct resource *res; > int i; > > - if (pci_is_root_bus(child)) /* It's a host bus, nothing to read */ > + /* > + * If it is not a PCI bridge there is nothing to read > + */ > + if (pci_is_root_bus(child) || !dev || > + !((dev->class >> 8) == PCI_CLASS_BRIDGE_PCI)) > return; > > dev_info(&dev->dev, "PCI bridge to %pR%s\n", > @@ -1878,6 +1882,11 @@ unsigned int pci_scan_child_bus(struct pci_bus *bus) > * all PCI-to-PCI bridges on this bus. > */ > if (!bus->is_added) { > + /* > + * Read and initialize bridge resources. > + */ > + pci_read_bridge_bases(bus); > + > dev_dbg(&bus->dev, "fixups for bus\n"); > pcibios_fixup_bus(bus); > bus->is_added = 1; >
So, I have tested the patch on ARM64 system w/ PROBE_ONLY mode, and noticed that we are calling pci_read_bridge_bases() after adding the devices on the slots. This is not soon enough since the downstream devices still failing to claim resources.
However, do you think we can move pci_read_bridge_bases() before the pci_scan_slot() loop?
Thanks, Suravee
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