On Tue, Jul 6, 2021 at 4:46 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> On Tue, 06 Jul 2021 15:30:34 +0100, Arnd Bergmann <arnd@xxxxxxxx> wrote:
> > I can only speculate on how much got reused between the two, but
> > as Falkor was released only after they had already given up on
> > the full-custom Kryo core, it's plausible that it incorporates bits from
> > that one. In particular the cache controller is probably easy to reuse
> > even if the rest of it was a new design.
>
> I guess we'll never find out, and I'm probably one of the few still
> having some access to this HW (not even sure for how long anyway).
>
> I won't cry if we decide to pull the plug on it.
Sure, but the Snapdragon 820E is one we do need to worry about.
While the internet pretty much agrees on Falkor having 128 bytes
L1 cache line, it might be good to rule out that Kryo just misreports
it before we revert the patch.
Yassine, could you run the 'line' and 'cache' helper from lmbench
to determine what the cache topology appears to be and if that
matches the CTR_EL0 contents?
Something like
numactl -C 0 line -M 1M
numactl -C 3 line -M 1M
numactl -C 0 cache
numactl -C 3 cache
(the numactl command helps run this both on the 'big' and 'little'
cores without running into migration)
Arnd
