[PATCH v3] [POWERPC] Add a comment about the Book-e tophys/tovirt macros

[Kumar Gala]

The Book-E versions of tophys/tovirt are not simple noops to
ensure compatibility with their "classic" ppc brethren.

---

Lets try this version based on paul's feedback.

 include/asm-powerpc/ppc_asm.h |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/include/asm-powerpc/ppc_asm.h b/include/asm-powerpc/ppc_asm.h
index 2dbd4e7..5499c13 100644
--- a/include/asm-powerpc/ppc_asm.h
+++ b/include/asm-powerpc/ppc_asm.h
@@ -356,6 +356,12 @@ END_FTR_SECTION_IFCLR(CPU_FTR_601)
 #define toreal(rd)
 #define fromreal(rd)

+/*
+ * We use addis to ensure compatibility with the "classic" ppc versions of
+ * these macros.  use rs = 0 to get the tophys offset in rd, rather than
+ * converting the address in r0, and so this version has to do that too
+ * (i.e. set register rd to 0 when rs == 0)
+ */
 #define tophys(rd,rs)				\
 	addis	rd,rs,0

-- 
1.5.4.5