bsp/atsam: Move clock and SDRAM init to SRAM.

If necessary, the BSP can now have it's clock and SDRAM initialization
in the SRAM instead of the SDRAM. This allows to change the clock
frequency during the startup of an SDRAM application.

1 files changed, 5 insertions, 2 deletions

diff --git a/c/src/lib/libbsp/arm/atsam/README b/c/src/lib/libbsp/arm/atsam/README
index e21e7ee405..c374e861c3 100644
--- a/c/src/lib/libbsp/arm/atsam/README
+++ b/c/src/lib/libbsp/arm/atsam/README
@@ -22,8 +22,11 @@ Use ATSAM_MCK=XYZ to set the MCK frequency that should be used. The default case
 evaluation kit. Some other configurations (e.g. 150MHz) would be too fast on
 that board.
 
-Your application can also overwrite the clock settings. To overwrite the clock
-settings, define the following structures in your application:
+Your application can also overwrite the clock settings.  If you have a
+bootloader with one setting in your internal flash and an application with
+another setting in your external SDRAM, you should also use the
+ATSAM_CHANGE_CLOCK_FROM_SRAM=1 option. To overwrite the clock settings, define
+the following structures in your application:
 
 --------
 const struct atsam_clock_config atsam_clock_config = {