[U-Boot] [PATCH 1/3 v2] 83xx: Default to using DMA to initializeSDRAM

[Peter Tyser]

On Thu, 2009-07-09 at 08:24 +0800, Liu Dave-R63238 wrote:
> > When SDRAM ECC is enabled and CONFIG_ECC_INIT_VIA_DDRCONTROLLER is not
> > defined use DMA to set SDRAM to a known state.  Previously a 
> > sequence of
> > 64-bit stores was used.
> 
> IIRC, the DMA init SDRAM is slower than the 64bit stores.
> It is why I added these code here.
> 
> I suggest to keep the way. 

According to Ira, the DMA method was faster than the cpu method:
"It makes the DMA initialization normal speed again. The DMA in the for
loop takes the longest (as expected).

So yes, strangely it (enabling the icache) makes a HUGE difference. The
total time is <3 seconds now. It is now faster than the previous CPU
method."


Logically the DMA method should be faster, and Ira's results seem to
reinforce this.  I don't have an 83xx board to test on, so let me know
if others have different results than Ira.

Best,
Peter