[U-Boot] AM335x: enabling datacache in SPL slows down system?

[Bas van den Berg]

Hi Jeroen,

After debugging a bit more, I found that in our code, we didn't set the RAM size
correctly (so no real RAM section was setup for caching). Fixing this fixed our
time to 2.4 seconds (U-boot still took 1.8 sec).

Adding your SRAM patch (modified, since AM335x has more SRAM),
The load time dropped from 2.4 -> 1.9 seconds. So adding this small area saved
half a second!
I write off the remaing difference (1.8 vs 1.9 seconds) to code differences between
our SPL and U-boot nand functions.

Thanks,
Bas

  _____  

From: Tom Rini [mailto:trini at ti.com]
To: Jeroen Hofstee [mailto:jeroen at myspectrum.nl]
Cc: Wolfgang Denk [mailto:wd at denx.de], bas.van.den.berg at alten.nl, u-boot at lists.denx.de
Sent: Fri, 21 Jun 2013 20:56:53 +0100
Subject: Re: [U-Boot] AM335x: enabling datacache in SPL slows down system?

On Fri, Jun 21, 2013 at 08:46:47PM +0200, Jeroen Hofstee wrote:
  
  > Hello Wolfgang,
  > 
  > On 06/21/2013 07:33 AM, Wolfgang Denk wrote:
  > >We observed the very same issue with the verry first prototype
  > >implementation of Falcon mode on an AM3517 based board. [..]
  > For the am3517 the only thing needed is to add SRAM
  > to the known memory. See [1], that should change the
  > cache misses (which likely cause the extra delays) to
  > actual caches. U-boot only adds the detected memory
  > and since U-boot is running from DRAM and SPL is not,
  > the difference seems obvious.
  
  This would be my guess as folks have done functional but not
  mainlineable changes in this direction, as well as DMA, before.
  
  -- 
  Tom