From mboxrd@z Thu Jan  1 00:00:00 1970
From: scaudle@codeaurora.org (Stephen Caudle)
Date: Thu, 16 Dec 2010 09:54:23 -0500
Subject: [PATCH v2] [ARM] gic: Unmask private interrupts on all cores
	during IRQ enable
In-Reply-To: <4D0102B3.8010302@codeaurora.org>
References: <1288820762-16077-1-git-send-email-scaudle@codeaurora.org>
	<20101130180718.GB8521@n2100.arm.linux.org.uk>
	<4CF6797A.2010807@codeaurora.org>
	<20101201171425.GA29347@n2100.arm.linux.org.uk>
	<4D0102B3.8010302@codeaurora.org>
Message-ID: <4D0A281F.1090705@codeaurora.org>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 12/09/2010 11:24 AM, Stephen Caudle wrote:
>> It is also unreasonable to have one core enabling the PPI on other
>> cores where the hardware behind the interrupt may not have been
>> initialized yet.  If it is a private interrupt for a private peripheral,
>> then only the associated CPU should be enabling that interrupt.
>>
>> I guess this is something which genirq can't cope with, in which case
>> either genirq needs to be modified to cope with private CPU interrupts,
>> which are controlled individually by their associated CPU, or we need a
>> private interface to support this.
> 
> I see your point.  Our immediate need for this is to support a
> performance monitor interrupt that happens to be a PPI.  It is used by
> perf events (and subsequently, oprofile).
> 
> Since PPIs are so machine-specific, I started looking into patching
> perf_events.c by adding a machine specific function to handle the PMU
> IRQ request.  For mach-msm, we would call request_irq like normal, but
> also unmask the performance monitor interrupt on the other cores.  The
> downside to this is that a machine specific implementation would be
> needed anytime a PPI is requested, not just in perf_events.c.
> 
> Then, I saw Thomas' email regarding our local timer PPI:
> http://lists.infradead.org/pipermail/linux-arm-kernel/2010-December/033840.html.
> 
> Russell, before I submit another patch, I would like to know if you
> prefer a more generic approach like Thomas suggests, or a
> machine-specific approach like I have described?

Russell, what are your thoughts on this?

Thanks,
Stephen

-- 
Sent by a consultant of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.