linux-kernel - Re: AMR: sun7i: CPU hotplug support?

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Message-ID: <5460554A.1060701@web.de>
Date:	Mon, 10 Nov 2014 07:03:54 +0100
From:	Jan Kiszka <jan.kiszka@....de>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>,
	Marc Zyngier <marc.zyngier@....com>
CC:	linux-arm-kernel@...ts.infradead.org, linux-sunxi@...glegroups.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: AMR: sun7i: CPU hotplug support?

On 2014-11-10 00:17, Maxime Ripard wrote:
> Hi Jan,
> 
> On Sun, Nov 09, 2014 at 08:35:49PM +0100, Jan Kiszka wrote:
>> did anyone already happen to look into enabling CPU hotplug for the
>> Allwinner A20 in upstream? I'm currently running the sunxi-next branch
>> on Banana Pi, and echo 0 > .../cpu1/online just hangs the system. The
>> old 3.4 LeMaker kernel works fine in this regard. I can try to look into
>> details and port things over, just want to avoid duplicate efforts.
> 
> Having hotplug support would indeed be very welcome.
> 
> However, it should be done in u-boot, through PSCI, and not in the
> kernel itself.
> 
> As far as I'm aware, no one worked actively on it, beside some WIP
> commit from Marc a while ago:
> https://git.kernel.org/cgit/linux/kernel/git/maz/u-boot.git/commit/?h=wip/psci&id=45379c0f9cf812f0f62722f4015ec907fa5dc144

OK - I guess I will need a little guidance in then: Is there a good
reference board to study and to derive from? And maybe also: What is
missing or not working in that u-boot branch? If I get this interface
right, I just takes some device tree bits to enable this for the kernel
afterward, correct?

Thanks,
Jan

PS: That the GMAC on B-Pi has some TX reliability issues, both with
kernel and u-boot, is known, right? If not, I'll open a separate thread.


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