[Linaro-validation] bigLITTLE needs more work

Peter Maydell peter.maydell at linaro.org
Wed Feb 15 00:44:25 UTC 2012

On 15 February 2012 00:33, Zygmunt Krynicki <zygmunt.krynicki at linaro.org> wrote:
> Prompted by Paul I've decided to try a bigLITTLE config. My test did
> not end up very good:
> 1) I've tried the RealView Express A15x1-A7x1 model

NB that I think the plan for big.LITTLE models is to use a prebuilt
RTSM, which should look the same as a binary built from the example
models, it's just a pre-cooked binary supplied by ARM rather than
built by us.

> 2) It has different options that can be passed to model shell, needles
> to say they are not compatible. I tweaked my semihosting line to look
> like this:
> -C coretile.cluster0.cpu0.semihosting-cmd_line="--kernel $KERNEL --
> console=ttyAMA0 mem=512M ip=dhcp root=/dev/nfs nfsroot=$NFSROOT,tcp rw
> earlyprintk $@"

Yeah, the parameters are specific to the components within the
model, so they vary depending on the structure of the model.

> 3) I did not get the kernel to boot at all, I suspect that our boot
> wrapper is not compatible or I mis-configured the kernel or something
> in between. I did not even get a X11 terminal window as I usually
> always get.

Yes, we've been clear for some time that the bootwrapper needs changes
to work with big.LITTLE (in fact I'm not entirely sure whether the
switcher code counts as part of the 'kernel' or not). Dave probably
knows more about the status here (I suspect there's some working
code somewhere, just maybe not in the git.linaro.org boot-wrapper
or whichever kernel you tried).

-- PMM

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