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@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: Michal Simek <monstr@xxxxxxxxx>
Cc: Koichi Yasutake <yasutake.koichi@xxxxxxxxxxxxxxxx>
Cc: Chris Zankel <chris@xxxxxxxxxx>
---
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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