linux-kernel - Re: [PATCH 0/2] arm: berlin: add cpu hotplug support

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Date:	Tue, 07 Jul 2015 09:28:34 +0200
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Jisheng Zhang <jszhang@...vell.com>, linux@....linux.org.uk
CC:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	antoine.tenart@...e-electrons.com
Subject: Re: [PATCH 0/2] arm: berlin: add cpu hotplug support

On 07/07/2015 09:10 AM, Jisheng Zhang wrote:
> These patches try to add cpu hotplug support for Marvell BG2, BG2Q SoCs.
> These SoCs can't power off cpu independently, but we still want cpu hotplug
> support for them. However, we need to address "CPU still sat on kernel text"
> as pointed out by Mark Rutland[1]. We achieved this by putting the dying CPU
> in WFI state after the coherency is disabled, then asserting the dying CPU
> reset bit to put the CPU in reset state.

Jisheng,

thanks for the patches! Out of curiosity, did you measure overall SoC 
power consumption with WFI and with reset respectively? I'd expect a
slightly _higher_ power consumption while in reset depending on clock
gating applied to the processor hardware.

Sebastian

> patch1 use non-self-cleared control register to reset cpu. This is to prepare
> for the next cpu hotplug commit.
>
> patch2 adds the cpu hotplug support finally.
>
>
> [1] http://lists.infradead.org/pipermail/linux-arm-kernel/2015-May/342642.html
>
> Jisheng Zhang (2):
>    arm: berlin: use non-self-cleared reset register to reset cpu
>    arm: berlin: add CPU hotplug support
>
>   arch/arm/mach-berlin/platsmp.c | 29 ++++++++++++++++++++++++++++-
>   1 file changed, 28 insertions(+), 1 deletion(-)
>
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