linux-kernel - Re: [RFC PATCH v2] Add IPI entry for CPU UP

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Date:	Tue, 12 Jan 2016 11:51:04 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Zhaoyang Huang (黄朝阳) 
	<zhaoyang.huang@...eadtrum.com>
Cc:	Zhaoyang Huang <zhaoyang.huang@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>, will.deacon@....com,
	linux-kernel@...r.kernel.org, Hanjun Guo <hanjun.guo@...aro.org>,
	suzuki.poulose@....com
Subject: Re: [RFC PATCH v2] Add IPI entry for CPU UP

On Tue, Jan 12, 2016 at 09:38:20AM +0000, Lorenzo Pieralisi wrote:
> On Tue, Jan 12, 2016 at 10:17:42AM +0800, Zhaoyang Huang wrote:
> > On 12 January 2016 at 10:05, Zhaoyang Huang <zhaoyang.huang@...aro.org> wrote:
> > > In some ARM SOCs, IPI interrupt is used for hotplug in one cpu, that is,
> > > sending a IPI to the core in WFI and powerdown status. So Add a IPI
> > > entry for handle this kind of cpu up interrupt
> > > Launching the IPI can be done within PSCI, while there will be one unknown
> > > type of IPI as the dest core come up to the kernel world which will bring a
> > > warning so far.So add such type of IPI to handle the interrupt.
> 
> You missed CC'ing ALKML for the second time and you were warned.
> 
> You are adding a call to *send* an IPI in the kernel so the commit
> above is misleading.
> 
> Acknowledge and clear the IRQ in FW so that the mechanism is completely
> implemented in FW (ie PSCI), that the CPU coming out of reset will run
> before getting to the kernel, this patch is not needed and we already
> explained to you why.
> 
> Lorenzo

I would also suggest that FW used the set of SGIs reserved for secure
usage (i.e. ID8 - ID15), as these will not conflict with those the
kernel uses.

Thanks,
Mark.