linux-kernel - Re: [PATCH] irqchip: irq-armada-370-xp: fix regression by clearing IRQ

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Message-ID: <20151021144110.GH3953@io.lakedaemon.net>
Date:	Wed, 21 Oct 2015 14:41:10 +0000
From:	Jason Cooper <jason@...edaemon.net>
To:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Marc Zyngier <marc.zyngier@....com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Tawfik Bayouk <tawfik@...vell.com>,
	Nadav Haklai <nadavh@...vell.com>,
	Lior Amsalem <alior@...vell.com>, Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>
Subject: Re: [PATCH] irqchip: irq-armada-370-xp: fix regression by clearing
 IRQ_NOAUTOEN

Hey Thomas-i, Thomases, :)

On Wed, Oct 21, 2015 at 03:48:15PM +0200, Thomas Petazzoni wrote:
> Commit d17cab4451df1 ("irqchip: Kill off set_irq_flags usage") changed
> the code of armada_370_xp_mpic_irq_map() from using set_irq_flags() to
> irq_set_probe().
> 
> While the commit log seems to imply that there are no functional
> changes, there are indeed functional changes introduced by this
> commit: the IRQ_NOAUTOEN flag is no longer cleared. This functional
> change causes a regression on Armada XP, which no longer works
> properly after suspend/resume because per-CPU interrupts remain
> disabled.
> 
> Due to how the hardware registers work, the irq-armada-370-xp cannot
> simply save/restore a bunch of registers at suspend/resume to make
> sure that the interrupts remain in the same state after
> resuming. Therefore, it relies on the kernel to say whether the
> interrupt is disabled or not, using the irqd_irq_disabled()
> function. This was all working fine while the IRQ_NOAUTOEN flag was
> cleared.
> 
> With the change introduced by Rob Herring in d17cab4451df1, the
> IRQ_NOAUTOEN flag is now set for all interrupts. irqd_irq_disabled()
> returns false for per-CPU interrupts, and therefore our per-CPU
> interrupts are no longer re-enabled after resume.
> 
> This commit works around this problem by clearing again the
> IRQ_NOAUTOEN flags, so that we are back to the situation we had before
> commit d17cab4451df1. This work around is proposed as a minimal fix
> for the problem, while a better long-term solution is being worked on.
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
> ---
> Here is the one-line minimal change that tglx said would be more
> acceptable to have in 4.3.
> ---
>  drivers/irqchip/irq-armada-370-xp.c | 1 +
>  1 file changed, 1 insertion(+)

Applied to irqchip/urgent with minor tweaking of the subject line.  I
trust at this point it's ok to pull in -rc2.

thx,

Jason.
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