nvrm transport: eliminate double-copying of messages

with the change to allocate messages < MAX_SIZE on the stack
inside the dispatcher, there were actually 2 on-stack copies
of the message being maintained: one in the dispatcher, and
one in the RM transport code itself.

the transport code copied the message in order to prepend
a 3-word header; however, since the entire message was then
copied into a memory handle to send it to the AVP, the
internal copy is unnecessary; the message header can be
written directly to the memory handle and then the buffer
provided by the dispatcher can be copied directly into
the memory handle

Change-Id: I3a748192d7e45445bc821456e170670cc3fb0e98

1 files changed, 8 insertions, 2 deletions

diff --git a/arch/arm/mach-tegra/nvos/nvos.c b/arch/arm/mach-tegra/nvos/nvos.c
index 3e98dfc03063..08f30ebb0d2f 100644
--- a/arch/arm/mach-tegra/nvos/nvos.c
+++ b/arch/arm/mach-tegra/nvos/nvos.c
@@ -349,9 +349,12 @@ void NvOsMemmove(void *dest, const void *src, size_t size)
 
 NvError NvOsCopyIn(void *pDst, const void *pSrc, size_t Bytes)
 {
+    if (!Bytes)
+        return NvSuccess;
+
     if( access_ok( VERIFY_READ, pSrc, Bytes ) )
     {
-        copy_from_user(pDst, pSrc, Bytes);
+        __copy_from_user(pDst, pSrc, Bytes);
         return NvSuccess;
     }
 
@@ -360,9 +363,12 @@ NvError NvOsCopyIn(void *pDst, const void *pSrc, size_t Bytes)
 
 NvError NvOsCopyOut(void *pDst, const void *pSrc, size_t Bytes)
 {
+    if (!Bytes)
+        return NvSuccess;
+
     if( access_ok( VERIFY_WRITE, pDst, Bytes ) )
     {
-        copy_to_user(pDst, pSrc, Bytes);
+        __copy_to_user(pDst, pSrc, Bytes);
         return NvSuccess;
     }