linux-kernel - Re: [linux-sunxi] [RFC 0/7] ARM: sun9i: SMP support with Multi-Cluster Power Management

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Date:	Tue, 19 May 2015 10:51:12 +0800
From:	Chen-Yu Tsai <wens@...e.org>
To:	Ian Campbell <ijc@...lion.org.uk>
Cc:	Chen-Yu Tsai <wens@...e.org>,
	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Dave Martin <Dave.Martin@....com>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-sunxi <linux-sunxi@...glegroups.com>
Subject: Re: [linux-sunxi] [RFC 0/7] ARM: sun9i: SMP support with
 Multi-Cluster Power Management

On Sat, May 16, 2015 at 6:08 PM, Ian Campbell <ijc@...lion.org.uk> wrote:
> On Thu, 2015-05-14 at 14:10 +0800, Chen-Yu Tsai wrote:
>> This is my attempt to support SMP and CPU hot plugging on the Allwinner
>> A80 SoC. The A80 is a big.Little processor with 2 clusters of 4x Cortex-A7
>> and 4x Cortex-A15 cores.
>
> I thought there was a preference these days to support this sort of
> thing via support PSCI in the firmware, which allows for other things
> such as non-secure-world etc.

Ideally, yes. However, U-boot only has minimal A80 support for now.
Also, multi-cluster support is not as simple as what we had for the
A20. The kernel already has common multi-cluster code. With it we
can do full SMP/hotplug support. Kernel code is also easier to write
and debug than PSCI, which ATM is all per-platform assembly.

Also, my A31 and A23 PSCI implementations still need some work.

ChenYu
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