Having a 'bus-range' property for PCI bridges should not be required,
so remove the warning when missing. There was some confusion with the
Linux kernel printing a message that no property is present and the OS
assigned the bus number. This message was intended to be informational
rather than a warning.
When the firmware doesn't enumerate the PCI bus and leaves it up to the
OS to do, then it is perfectly fine for the OS to assign bus numbers
and bus-range is not necessary.
There are a few cases where bus-range is needed or useful as Arnd
Bergmann summarized:
- Traditionally Linux avoided using multiple PCI domains, but instead
configured separate PCI host bridges to have non-overlapping
bus ranges so we can present them to user space as a single
domain, and run the kernel without CONFIG_PCI_DOMAINS.
Specifying the bus ranges this way would and give stable bus
numbers across boots when the probe order is not fixed.
- On certain ARM64 systems, we must only use the first
128 bus numbers based on the way the IOMMU identifies
the device with truncated bus/dev/fn number. There are probably
others like this, with various limitations.
- To leave some room for hotplugged devices, each slot on
a host bridge can in theory get a range of bus numbers
that are available when assigning bus numbers at boot time
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
---
v2:
- expand the commit message about when bus-range is used or not
checks.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/checks.c b/checks.c
index 1e6a88c81a99..261c57557ad2 100644
--- a/checks.c
+++ b/checks.c
@@ -792,10 +792,9 @@ static void check_pci_bridge(struct check *c, struct dt_info *dti, struct node *
FAIL(c, dti, node, "incorrect #size-cells for PCI bridge");
prop = get_property(node, "bus-range");
- if (!prop) {
- FAIL(c, dti, node, "missing bus-range for PCI bridge");
+ if (!prop)
return;
- }
+
if (prop->val.len != (sizeof(cell_t) * 2)) {
FAIL_PROP(c, dti, node, prop, "value must be 2 cells");
return;
--
2.14.1
--
To unsubscribe from this list: send the line "unsubscribe devicetree-compiler" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
