powerpc/mpic: Add "last-interrupt-source" property to override hardware

The FreeScale PowerQUICC-III-compatible (mpc85xx/mpc86xx) MPICs do not
correctly report the number of hardware interrupt sources, so software
needs to override the detected value with "256".

To avoid needing to write custom board-specific code to detect that
scenario, allow it to be easily overridden in the device-tree.

Signed-off-by: Kyle Moffett <Kyle.D.Moffett@boeing.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/powerpc/fsl/mpic.txt b/Documentation/devicetree/bindings/powerpc/fsl/mpic.txt
index b393ccf1e9f3..dc5744636a57 100644
--- a/Documentation/devicetree/bindings/powerpc/fsl/mpic.txt
+++ b/Documentation/devicetree/bindings/powerpc/fsl/mpic.txt
@@ -70,6 +70,13 @@ PROPERTIES
           If present the MPIC will be assumed to only be able to route
           non-IPI interrupts to a single CPU at a time (EG: Freescale MPIC).
 
+  - last-interrupt-source
+      Usage: optional
+      Value type: <u32>
+          Some MPICs do not correctly report the number of hardware sources
+          in the global feature registers.  If specified, this field will
+          override the value read from MPIC_GREG_FEATURE_LAST_SRC.
+
 INTERRUPT SPECIFIER DEFINITION
 
   Interrupt specifiers consists of 4 cells encoded as