linux-kernel - Re: [PATCH] arm: perf: Directly handle SMP platforms with one SPI

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Date:	Tue, 2 Dec 2014 14:22:33 +0100
From:	Linus Walleij <linus.walleij@...aro.org>
To:	Daniel Thompson <daniel.thompson@...aro.org>
Cc:	Russell King <linux@....linux.org.uk>,
	Will Deacon <will.deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Shawn Guo <shawn.guo@...aro.org>,
	Sascha Hauer <kernel@...gutronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lucas Stach <l.stach@...gutronix.de>,
	Patch Tracking <patches@...aro.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	John Stultz <john.stultz@...aro.org>,
	Sumit Semwal <sumit.semwal@...aro.org>
Subject: Re: [PATCH] arm: perf: Directly handle SMP platforms with one SPI

On Fri, Nov 21, 2014 at 3:53 PM, Daniel Thompson
<daniel.thompson@...aro.org> wrote:

> Some ARM platforms mux the PMU interrupt of every core into a single
> SPI. On such platforms if the PMU of any core except 0 raises an interrupt
> then it cannot be serviced and eventually, if you are lucky, the spurious
> irq detection might forcefully disable the interrupt.
>
> On these SoCs it is not possible to determine which core raised the
> interrupt so workaround this issue by queuing irqwork on the other
> cores whenever the primary interrupt handler is unable to service the
> interrupt.
>
> The u8500 platform has an alternative workaround that dynamically alters
> the affinity of the PMU interrupt. This workaround logic is no longer
> required so the original code is removed as is the hook it relied upon.
>
> Tested on imx6q (which has fours cores/PMUs all muxed to a single SPI).
>
> Signed-off-by: Daniel Thompson <daniel.thompson@...aro.org>

After som pain I managed to compile and test this with perf.
Works like a charm.

Tested-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij
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