linux-kernel - Re: [PATCH] mfd: add MAX8907 core driver

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Message-ID: <20120726221604.GL4560@opensource.wolfsonmicro.com>
Date:	Thu, 26 Jul 2012 23:16:04 +0100
From:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	Samuel Ortiz <sameo@...ux.intel.com>,
	Laxman Dewangan <ldewangan@...dia.com>,
	Liam Girdwood <lrg@...com>, linux-kernel@...r.kernel.org,
	devicetree-discuss@...ts.ozlabs.org,
	Gyungoh Yoo <jack.yoo@...im-ic.com>,
	Stephen Warren <swarren@...dia.com>
Subject: Re: [PATCH] mfd: add MAX8907 core driver

On Thu, Jul 26, 2012 at 04:07:12PM -0600, Stephen Warren wrote:
> On 07/26/2012 02:35 PM, Mark Brown wrote:
> > On Thu, Jul 26, 2012 at 01:40:30PM -0600, Stephen Warren wrote:

> >> +		if (irqd_is_wakeup_set(d)) {
> >> +			/* 1 -- disable, 0 -- enable */
> >> +			switch (irq_data->mask_reg) {

> > This loop we should just port over into the regmap code.

> I assume the best way of doing this is to add new functions
> regmap_irq_suspend()/regmap_irq_resume() (which would mask any enabled
> interrupts that were not wake enabled); that way, the regmap_irq code
> can loop over each register and just write it once. An alternative might
> be to implement struct irq_chip's .irq_suspend/.irq_resume ops, but that
> might worst-case end up with an I2C write per interrupt.

irq_suspend() and irq_resume() are only supposed to be called once per
irq_chip so there should be no concern with using them.  Even if they
weren't it's probably not that performance critical really.

> I see that the MAX8907 IRQ code does this in suspend:

> 	if (device_may_wakeup(chip->dev))
> 		enable_irq_wake(i2c->irq);
> 	else
> 		disable_irq(i2c->irq);

> and this in resume:

> 	if (device_may_wakeup(chip->dev))
> 		disable_irq_wake(i2c->irq);
> 	else
> 		enable_irq(i2c->irq);

> neither of which are done in regmap_irq, since it doesn't explicitly do
> anything for suspend/resume at the moment. Are those code blocks
> necessary? I see that regmap_irq_sync_unlock() is already calling
> irq_set_irq_wake(), which implies that suspend/resume may have already
> been completely taken care of?

Yes, it should already be taken care of.  What the calls here are doing
is mostly allowing userspace to explicitly override the wake state on a
per chip basis.  I'm not convinced it's terribly clever to implement
explicit wake support on an interrupt controller, it seems prone to
confusion.  We could do that though.

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