Introduce arch_phys_memset which works like memset but on physical memory

The default implementation of this function is just memset, but other
implementations will be needed when physical memory isn't accessible by
U-Boot using normal addressing mechanisms.

Signed-off-by: Gabe Black <gabeblack@chromium.org>
Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/README b/README
index ed7d270adb..c7aab18efa 100644
--- a/README
+++ b/README
@@ -2200,6 +2200,14 @@ CBFS (Coreboot Filesystem) support
                         HERMES, IP860, RPXlite, LWMON,
                         FLAGADM, TQM8260
 
+- Access to physical memory region (> 4GB)
+                Some basic support is provided for operations on memory not
+                normally accessible to U-Boot - e.g. some architectures
+                support access to more than 4GB of memory on 32-bit
+                machines using physical address extension or similar.
+                Define CONFIG_PHYSMEM to access this basic support, which
+                currently only supports clearing the memory.
+
 - Error Recovery:
                 CONFIG_PANIC_HANG