linux-kernel - Re: [PATCH] pinctrl: rockchip: Only mask interrupts; never disable

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Date:	Mon, 26 Jan 2015 17:56:19 +0100
From:	Heiko Stübner <heiko@...ech.de>
To:	Doug Anderson <dianders@...omium.org>
Cc:	Linus Walleij <linus.walleij@...aro.org>,
	Jeffy Chen <jeffy.chen@...k-chips.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pinctrl: rockchip: Only mask interrupts; never disable

Am Montag, 26. Januar 2015, 08:24:03 schrieb Doug Anderson:
> The Rockchip GPIO interrupt controller totally throws away all status
> about an interrupt when you "disable" the interrupt.  That has
> unfortunate consequences in the following situation:
> 
> 1. An edge-triggered interrupt is enabled and should wake the system.
> 2. System suspend happens: interrupt is disabled and marked for wake.
> 3. rockchip_irq_suspend() reenables the interrupt so we can wake.
> 4. Interrupt happens when asleep.
> 5. rockchip_irq_resume() redisables the interrupt.
> 6. Disabling the interrupt throws away all status about it.
> 7. Normal system resume happens and we enable the interrupt again,
>    since we threw away status about the interrupt we don't know it
>    fired while suspended.  Even worse: if we need both edges of the
>    interrupt the logic to swap edges never runs.
> 
> Note: even if we somehow can post the status about wakeup interrupts
> in rockchip_irq_resume() we would still have a window of losing any
> edges that came in while interrupts were disabled.
> 
> If we use mask only then we don't need to worry.  The GPIO Interrupt
> controller keeps track of pending interrupts that are enabled and just
> masked.
> 
> There was no real strong reason to support the enable/disable
> functionality (other than that it seemed right), so let's go back to
> just supporting mask/unmask but actually map it to the real
> mask/unmask.  This ends up with slightly different (and more correct)
> behavior than before (f2dd028 pinctrl: rockchip: Fix
> enable/disable/mask/unmask).
> 
> Signed-off-by: Doug Anderson <dianders@...omium.org>

I talked with Doug about it and this looks sane, so
Reviewed-by: Heiko Stuebner <heiko@...ech.de>


Heiko
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