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Message-ID: <50533D46.5000704@arm.com>
Date: Fri, 14 Sep 2012 15:20:54 +0100
From: Marc Zyngier <marc.zyngier@arm.com>
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To: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: "arnd@arndb.de" <arnd@arndb.de>,
        "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
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        Ian Campbell <Ian.Campbell@citrix.com>,
        "konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
        Catalin Marinas <Catalin.Marinas@arm.com>,
        "Tim (Xen.org)" <tim@xen.org>,
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        "linux@arm.linux.org.uk" <linux@arm.linux.org.uk>,
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	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v4 16/24] xen: clear IRQ_NOAUTOEN and IRQ_NOREQUEST
References: <alpine.DEB.2.02.1209141145150.29232@kaball.uk.xensource.com> <1347621207-11294-16-git-send-email-stefano.stabellini@eu.citrix.com> <505338E6.4050504@arm.com> <alpine.DEB.2.02.1209141508130.29232@kaball.uk.xensource.com>
In-Reply-To: <alpine.DEB.2.02.1209141508130.29232@kaball.uk.xensource.com>
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On 14/09/12 15:13, Stefano Stabellini wrote:
> On Fri, 14 Sep 2012, Marc Zyngier wrote:
>> On 14/09/12 12:13, Stefano Stabellini wrote:
>>> Reset the IRQ_NOAUTOEN and IRQ_NOREQUEST flags that are enabled by
>>> default on ARM. If IRQ_NOAUTOEN is set, __setup_irq doesn't call
>>> irq_startup, that is responsible for calling irq_unmask at startup time.
>>> As a result event channels remain masked.
>>>
>>> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>>> Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>> ---
>>>  drivers/xen/events.c |    1 +
>>>  1 files changed, 1 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/xen/events.c b/drivers/xen/events.c
>>> index 5ecb596..8ffb7b7 100644
>>> --- a/drivers/xen/events.c
>>> +++ b/drivers/xen/events.c
>>> @@ -836,6 +836,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
>>>  		struct irq_info *info = info_for_irq(irq);
>>>  		WARN_ON(info == NULL || info->type != IRQT_EVTCHN);
>>>  	}
>>> +	irq_clear_status_flags(irq, IRQ_NOREQUEST|IRQ_NOAUTOEN);
>>
>> This one just sent a shiver down my spine. Are you doing this for a PPI?
> 
> Not really: even though there is just one source of event notifications
> (that is a PPI), we have many event channels. When a domain receives a
> notification (via the PPI), it checks on a bitmask to which event channel
> it corresponds. From the Linux point of view every event channel is a
> Linux irq belonging to the xen_dynamic_chip (see
> drivers/xen/events.c:xen_dynamic_chip).
> 
> So here I am not doing this for the one PPI, but I am doing this for
> every Linux irq (of chip xen_dynamic_chip) that represents an event
> channel.

So this is some sort of secondary interrupt controller, cascaded into
your GIC emulation, and this patch only affects the xen_dynamic_chip?

	M.
-- 
Jazz is not dead. It just smells funny...