[PATCH] ARM: multi_v7_defconfig: major refresh

Kevin Hilman
2014-08-08T18:04:02Z

Olof Johansson <olof@lixom.net> writes:

> On Fri, Aug 1, 2014 at 4:01 AM, Jon Medhurst (Tixy) <tixy@linaro.org> wrote:
>> On Fri, 2014-08-01 at 11:26 +0100, Sudeep Holla wrote:
>>>
>>> On 22/07/14 19:01, Olof Johansson wrote:
>>> > This is a major refresh of the multi_v7_defconfig:
>>> >
>>> > - Bring over a bunch of Samsung drivers to make ODROID-U3 and Chromebooks usable
>>> > * Enable big.LITTLE
>>> > * MCPM
>>> [...]
>>
>>> > +CONFIG_BIG_LITTLE=y
>>> > +CONFIG_BL_SWITCHER=y
>>>
>>> IIUC, this will enable switcher code by default. I am not sure if this
>>> is intentional ? E.g.: After this I can have only 2 active cpus instead
>>> of 5 on my Vexpress TC2 platform.
>>>
>>> IMO we can keep this enabled by default in the build, but disabled
>>> by default on boot.
>>
>> TC2 has a big.LITTLE processor and the switcher is the only mainlined
>> way of making any kind of proper use of big.LITTLE, so why not have it
>> enabled by default?
>
> +1.
>

I disagree.

The bL switcher is a stopgap used on products (which have their own
defconfigs anyways) but upstream development is focused on HMP (or
whatever the current buzzword is for the kernel directly scheduling both
big and little cores.)

So IMO, for upstream coverage, we should *not* be enabling the switcher
but should be letting the scheduler directly manage all CPUs.

At least on Exynos, with MCPM support merged, the kernel can boot up all
the CPUs and directly manage them.

Kevin