On Thu, Jun 30, 2011 at 11:54 AM, Raleigh Boulware r_boulware@hotmail.com wrote:
Hi Raleigh,
On Thu, Jun 30, 2011 at 11:16 AM, Raleigh Boulware r_boulware@hotmail.com wrote:
I have been going through the code and I have stumbled accross a file called sc520_car.S that has something called Cache as ram. I am guessing that this is something special for the sc520 correct? Why was there a need to do this? Why was the Cache used like ram in the boot process?
Cache-As-RAM allows the CPU cache to be used as regular RAM while U-Boot is running from Flash before the onboard SDRAM has been initialised. This allows a temporary stack, and therefore C runtime environment to be created. This this allows you to write the SDRAM initialisation code in C which is a lot easier than assembler.
So this is pnly used if we want to setup the SDRAM controller in C code
More that just that - It is used for the duration of board_init_f() which may include all manner of peripheral initialisation prior to relocating U-Boot into RAM.
correct? In this code it is not used because the SDRAM cotroller is pretty much working from power up. So when I port this to my motherboard it looks as if i really do not need this.. Am I correct in this thinking??
You may need to initialise the SDRAM controller - It really depends on the underlying hardware. You are going to need to have a good look at the technical documentation for your board to figure this one out
Regards,
Graeme