[OpenBIOS] [PATCH 3/4 v3] arch/ppc/qemu: Add a node for the other (empty) PCI bus to the device tree

BALATON Zoltan balaton at eik.bme.hu
Tue Jan 31 14:50:41 CET 2017

QEMU emulates two of the three PCI buses found on real hardware because
some clients seem to need both and fail with only one present, but
OpenBIOS only handles a single PCI bus and initialises and puts in the
device tree only one of these: the second one which is where devices are
connected and also marks it bus 0. However, clients getting info from the
device tree may not know about this and thinking there is only one PCI
bus they erroneously use the address of the first bus to access PCI
config registers for devices on the second bus which silently fails as
these requests will go to the other empty bus emulated and return invalid
values. Devices mapped via MMIO still appear to work but they may not be
correctly initialised and some cards are not detected because of this.

Until support for multiple PCI buses is implemented add an empty node in
the device tree for the uninitialised bus to let clients know about it.
This is still not entirely correct as bus-range property does not match
real hardware but this fixes detecting PCI devices (such as USB) under
MorphOS and may also fix enabling the bus master bit needed with some
network cards and allow the workaround for this to be reverted.

Signed-off-by: BALATON Zoltan <balaton at eik.bme.hu>
 arch/ppc/qemu/init.c | 43 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)

v3: Move device tree patching in its own function and call it from
init (otherwise same as v2, take which you like)

v2: Move to init.c from tree.fs and only add it for mac99
Patches 1 and 2 from original series
are still valid and needed, patch 4 was already applied so only this
one (3/4) is resent but 1 and 2 should be applied as well with this.

diff --git a/arch/ppc/qemu/init.c b/arch/ppc/qemu/init.c
index ffbf08d..46a56a0 100644
--- a/arch/ppc/qemu/init.c
+++ b/arch/ppc/qemu/init.c
@@ -668,6 +668,48 @@ static void kvm_of_init(void)
+static void empty_pci_bus_init(void)
+    if (machine_id == ARCH_MAC99) {
+        /* Add empty node for first pci bus */
+        /* Remove this when pci driver is fixed to handle multiple buses */
+        activate_device("/");
+        fword("new-device");
+        push_str("pci");
+        fword("device-name");
+        push_str("pci");
+        fword("device-type");
+        PUSH(0xf0000000);
+        fword("encode-int");
+        PUSH(0x02000000);
+        fword("encode-int");
+        fword("encode+");
+        push_str("reg");
+        fword("property");
+        PUSH(3);
+        fword("encode-int");
+        push_str("#address-cells");
+        fword("property");
+        PUSH(2);
+        fword("encode-int");
+        push_str("#size-cells");
+        fword("property");
+        PUSH(1);
+        fword("encode-int");
+        push_str("#interrupt-cells");
+        fword("property");
+        PUSH(0);
+        fword("encode-int");
+        PUSH(0);
+        fword("encode-int");
+        fword("encode+");
+        push_str("bus-range");
+        fword("property");
+        fword("finish-device");
+        device_end();
+    }
  *  filll        ( addr bytes quad -- )
@@ -755,6 +797,7 @@ arch_of_init(void)
+    empty_pci_bus_init();

More information about the OpenBIOS mailing list