[PATCH] ARM: clean-up common multi-platform kconfig options
arnd at arndb.de
Sat Dec 7 22:39:45 EST 2013
On Saturday 07 December 2013, Russell King - ARM Linux wrote:
> So, as far as I'm aware, today, a kernel which has V6, V6K and V7
> will work across all those CPUs.
> What's rather annoying in this thread is that you and Arnd are running
> around seemingly making decisions on this without bothering to find out
> the details, in persuit of endless cleanups. Where is this heading?
I admit that we've been stumbling a bit in the dark at some points, but
that doesn't mean every idea ends up in a patch that even gets submitted.
What I've concluded so far is (please correct any statements that you
find are wrong):
* there is no harm in "select HAVE_SMP if CPU_V7" for multiplatform, as
was the original suggestion. Whether we want to actually do that is
open for discussion when someone submits a patch.
* It was a mistake (I guess mine) to 'select CPU_V6' from ARCH_MULTI_V6,
since that makes V6K based platforms slower without a reason, and we
probably want to do something else.
* A kernel which enables V6, V6K and V7 has a broken kuser_cmpxchg64
implementation on pre-V6K CPUs.
* Most platforms (possibly every one but OMAP2) that select CPU_V6
today are actually V6K compatible. It's probably worth asking those
V6 platform maintainers to change their CPU selection after confirming
that they are V6K-only.
* I'm still trying to understand the full implications of
CONFIG_CPU_USE_DOMAIN, but according to the comment in 247055aa21ffe
"ARM: 6384/1: Remove the domain switching on ARMv6k/v7 CPUs", it seems
to be a bug to enable this on v6k or v7 CPUs, which we currently do
whenever CPU_V6 (implied by CONFIG_MULTI_V6) is enabled.
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