From mboxrd@z Thu Jan  1 00:00:00 1970
From: zhanzhenbo@gmail.com (Steve zhan)
Date: Fri, 11 Jan 2013 18:24:16 +0800
Subject: Question:add
Message-ID: <20130111102416.GA18438@android11.spreadtrum.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

All:
	I have find that arm gic driver have not register irq_disable
method, as below:
static struct irq_chip gic_chip = {
	.name			= "GIC",
	.irq_mask		= gic_mask_irq,
	.irq_unmask		= gic_unmask_irq,
	.irq_eoi		= gic_eoi_irq,
	.irq_set_type		= gic_set_type,
	.irq_retrigger		= gic_retrigger,
#ifdef CONFIG_SMP
	.irq_set_affinity	= gic_set_affinity,
#endif
	.irq_set_wake		= gic_set_wake,
};

Question is: 
	When some drivers want to disable irq, maybe it will call 
linux standard inerface: irq_disable() that defined in include\
linux\interrupt.h, this function will call
void irq_disable(struct irq_desc *desc)
{
	irq_state_set_disabled(desc);
	if (desc->irq_data.chip->irq_disable) {
		desc->irq_data.chip->irq_disable(&desc->irq_data);
		irq_state_set_masked(desc);
	}
}

Because gic have not register irq_diable method, so the interrupt can
not disable immediately, it is enable until the interrupt come next time,
then disalbed by mask because irq_state_set_disable(desc);

I have checked irq_enable method:
void irq_enable(struct irq_desc *desc)
{
	irq_state_clr_disabled(desc);
	if (desc->irq_data.chip->irq_enable)
		desc->irq_data.chip->irq_enable(&desc->irq_data);
	else
		desc->irq_data.chip->irq_unmask(&desc->irq_data);
	irq_state_clr_masked(desc);
}
This method have do unmask when irq_enable method is not exist.

Is it a good idea to add irq_mask call in irq_disable()?


Regards,
Steve