[SLOF] [PATCH 1/3] Fix bad interrupt pin numbering in interrupt-map property of PCI bridges

[Thomas Huth]

The legacy PCI interrupts in the device tree are enumerated from 1
to 4. However, the code in pci-gen-irq-map-one generates numbers
between 0 and 3 instead. This renders devices unusable by Linux
in case they should use IRQ 4. For example, when starting QEMU with

 qemu-system-ppc64 ... \
    -device pci-bridge,bus=pci.0,id=bridge1,chassis_nr=1,addr=0x6 \
    -device virtio-balloon-pci,id=balloon0,bus=bridge1,addr=3

Linux can not use the balloon device since it is unable to determine
the right IRQ number in this case.
To fix this issue, we've simply got to make sure that the IRQ
numbers are in the range from 1 to 4 instead of 0 to 3.

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1366953
Signed-off-by: Thomas Huth <thuth at redhat.com>
---
 board-qemu/slof/pci-interrupts.fs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/board-qemu/slof/pci-interrupts.fs b/board-qemu/slof/pci-interrupts.fs
index e11b779..aec1106 100644
--- a/board-qemu/slof/pci-interrupts.fs
+++ b/board-qemu/slof/pci-interrupts.fs
@@ -1,6 +1,6 @@
 
 : pci-gen-irq-map-one ( prop-addr prop-len slot pin -- prop-addr prop-len )
-        2dup + 4 mod                ( prop-addr prop-len slot pin parentpin )
+        2dup + 1- 3 and 1+          ( prop-addr prop-len slot pin parentpin )
         >r >r                       ( prop-addr prop-len slot R: swizzledpin pin )
 
         \ Child slot#
-- 
1.8.3.1