4 files changed, 27 insertions, 2 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
diff --git a/arch/powerpc/platforms/pasemi/Kconfig b/arch/powerpc/platforms/pasemi/Kconfig
index 95cd90fd81c7..117d90aa5008 100644
--- a/arch/powerpc/platforms/pasemi/Kconfig
+++ b/arch/powerpc/platforms/pasemi/Kconfig
@@ -5,6 +5,7 @@ config PPC_PASEMI
         select MPIC
         select PPC_UDBG_16550
         select PPC_NATIVE
+        select MPIC_BROKEN_REGREAD
         help
           This option enables support for PA Semi's PWRficient line
           of SoC processors, including PA6T-1682M
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 25a81f73cecf..8de29f28b4c7 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -228,8 +228,13 @@ static inline u32 _mpic_irq_read(struct mpic *mpic, unsigned int src_no, unsigne
         unsigned int    isu = src_no >> mpic->isu_shift;
         unsigned int    idx = src_no & mpic->isu_mask;
 
-        return _mpic_read(mpic->reg_type, &mpic->isus[isu],
-                          reg + (idx * MPIC_INFO(IRQ_STRIDE)));
+#ifdef CONFIG_MPIC_BROKEN_REGREAD
+        if (reg == 0)
+                return mpic->isu_reg0_shadow[idx];
+        else
+#endif
+                return _mpic_read(mpic->reg_type, &mpic->isus[isu],
+                                  reg + (idx * MPIC_INFO(IRQ_STRIDE)));
 }
 
 static inline void _mpic_irq_write(struct mpic *mpic, unsigned int src_no,
@@ -240,6 +245,11 @@ static inline void _mpic_irq_write(struct mpic *mpic, unsigned int src_no,
 
         _mpic_write(mpic->reg_type, &mpic->isus[isu],
                     reg + (idx * MPIC_INFO(IRQ_STRIDE)), value);
+
+#ifdef CONFIG_MPIC_BROKEN_REGREAD
+        if (reg == 0)
+                mpic->isu_reg0_shadow[idx] = value;
+#endif
 }
 
 #define mpic_read(b,r)          _mpic_read(mpic->reg_type,&(b),(r))
diff --git a/include/asm-powerpc/mpic.h b/include/asm-powerpc/mpic.h
index 0eb3ab9ec2bb..edb4a7c84506 100644
--- a/include/asm-powerpc/mpic.h
+++ b/include/asm-powerpc/mpic.h
@@ -306,6 +306,10 @@ struct mpic
         unsigned long           *hwirq_bitmap;
 #endif
 
+#ifdef CONFIG_MPIC_BROKEN_REGREAD
+        u32                     isu_reg0_shadow[MPIC_MAX_IRQ_SOURCES];
+#endif
+
         /* link */
         struct mpic             *next;