[POWERPC] Add workaround for MPICs with broken register reads

Some versions of PWRficient 1682M have an interrupt controller in which
the first register in each pair for interrupt sources doesn't always
read with the right polarity/sense values.

To work around this, keep a software copy of the register instead.  Since
it's not modified from the mpic itself, it's a feasible solution.  Still,
keep it under a config option to avoid wasting memory on other platforms.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

1 files changed, 10 insertions, 0 deletions

diff --git a/arch/powerpc/platforms/Kconfig b/arch/powerpc/platforms/Kconfig
index 065f3b19d6c7..78a7edac577f 100644
--- a/arch/powerpc/platforms/Kconfig
+++ b/arch/powerpc/platforms/Kconfig
@@ -137,6 +137,16 @@ config MPIC_U3_HT_IRQS
         depends on PPC_MAPLE
         default y
 
+config MPIC_BROKEN_REGREAD
+        bool
+        depends on MPIC
+        help
+          This option enables a MPIC driver workaround for some chips
+          that have a bug that causes some interrupt source information
+          to not read back properly. It is safe to use on other chips as
+          well, but enabling it uses about 8KB of memory to keep copies
+          of the register contents in software.
+
 config IBMVIO
         depends on PPC_PSERIES || PPC_ISERIES
         bool