[U-Boot] Testing Data Cache for armv7 (beagleboard)

[chris c]

Thanks for the replies.  I didn't realize that the MMC module was operating
in 1-bit mode inside U-boot.  I'll concentrate on looking at that.  Has
anybody done any work to try and get 4-bit mode working for OMAP3 in U-boot?

Thanks,
Chris

On Thu, Oct 7, 2010 at 1:04 PM, Wolfgang Denk <wd at denx.de> wrote:

> Dear chris c,
>
> In message <AANLkTi=usuEyf4YuUVWrrLu80bMRFpRF+BThEix2bFNg at mail.gmail.com<usuEyf4YuUVWrrLu80bMRFpRF%2BBThEix2bFNg at mail.gmail.com>>
> you wrote:
> >
> > I was comparing time just by timing it manually.  How did you instrument
> > u-boot to display the time?
>
> That's no instrumentation of U-Boot, but just timestamping the output
> on the serial console. See for example
> ftp://ftp.denx.de/pub/tools/time_log
>
> > As for the small versus large file, I did the same test for 1MB of data
> > using nand read and saw a x4 performance advantage.  I also did a test on
> > mmc with 100 MB file and saw no performance increase.  Looks like file
> size
> > doesn't matter.
> >
> > So does that mean that MMC file loading will not benefit from dcache
> > enabled?  Can anybody explain this?
>
> It depends on where the time is actually spent. If you have a slow
> (say, bit-banging) MMC driver and a low-performance CPU then the
> transfer from MMC might simply not depend as much on caches. It is
> wrong to check just a simple use case. Try a number of different
> operations, like umcompressing a large image in RAM or from NOR to
> RAM, or downloading over the net, or ...
>
> Best regards,
>
> Wolfgang Denk
>
> --
> DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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>