On Thu, 8 Jan 2015, Boris Brezillon wrote:

1) Is it close to what you had in mind ?

Yes.

2) I'm not sure which part of the code should go where, so don't hesitate
   to point out misplaced sections.

Looks sane. Nits below.

3) Do I need to disable the source irq (the one feeding the irqchip) when
   entering suspend (and enable it on resume) ?

That probably needs to be part of the dumb mask/unmask functions.,
i.e. if no demux interrupt is enabled, the source irq should be
masked.

4) I'm not sure of what flags should be set/cleared when mapping an
   interrupt. Should I let the caller decide of this config (something
   similar to what is done in generic-chip) ?

I don't think you need to set/clear anything. Lets look at that dumb
demux chip as a real electronic circuit

     	     	  |----------------|
		  |                |
     	     	  |  --|Unmasked|--|---- Demux0
		  |  |             |
     SRC irq -----|-- -|Unmasked|--|---- Demux1
		  |  |             |
     	     	  |  --|Unmasked|--|---- Demux2
		  |                |
     	     	  |----------------|

Whether a demultiplexed interrupt is mapped or not is not really
important. The only relevant information is whether its masked or
not. So the default state is masked until a demultiplexed interrupt
gets requested.

+/**
+ * enum irq_dumb_demux_flags - Initialization flags for generic irq chips
+ * @IRQ_DD_INIT_NESTED_LOCK:	Set the lock class of the irqs to nested for
+ *				irq chips which need to call irq_set_wake() on
+ *				the parent irq. Usually GPIO implementations
+ */
+enum irq_dumb_demux_flags {
+	IRQ_DD_INIT_NESTED_LOCK		= 1 << 0,
+};
+
+/**
+ * struct irq_chip_dumb_demux - Dumb demultiplexer irq chip data structure
+ * @domain:		irq domain pointer
+ * @max_irq:		Last valid irq
+ * @available:		Bitfield of valid irqs
+ * @unmasked:		Bitfield containing irqs status
+ * @flags:		irq_dumb_demux_flags flags
+ *
+ * Note, that irq_chip_generic can have multiple irq_chip_type
+ * implementations which can be associated to a particular irq line of
+ * an irq_chip_generic instance. That allows to share and protect
+ * state in an irq_chip_generic instance when we need to implement
+ * different flow mechanisms (level/edge) for it.
+ */
+struct irq_chip_dumb_demux {
+	struct irq_domain *domain;
+	int max_irq;
+	unsigned long *available;
+	unsigned long *unmasked;

Why pointers? A single ulong is certainly enough.

+/**
+ *	handle_dumb_demux_irq - Dumb demuxer irq handle function.
+ *	@irq:	the interrupt number
+ *	@desc:	the interrupt description structure for this irq
+ *
+ *	Dumb demux interrupts are sent from a demultiplexing interrupt handler
+ *	which is not able to decide which child interrupt interrupt handler
+ *	should be called.
+ *
+ *	Note: The caller is expected to handle the ack, clear, mask and
+ *	unmask issues if necessary.
+ */
+irqreturn_t
+handle_dumb_demux_irq(unsigned int irq, struct irq_desc *desc)
+{
+	irqreturn_t retval = IRQ_NONE;
+
+	raw_spin_lock(&desc->lock);
+
+	if (!irq_may_run(desc))
+		goto out_unlock;
+
+	desc->istate &= ~(IRQS_REPLAY | IRQS_WAITING);
+	kstat_incr_irqs_this_cpu(irq, desc);
+
+	if (unlikely(!desc->action || irqd_irq_disabled(&desc->irq_data))) {
+		desc->istate |= IRQS_PENDING;
+		goto out_unlock;
+	}
+
+	retval = handle_irq_event_no_spurious_check(desc);
+
+out_unlock:
+	raw_spin_unlock(&desc->lock);
+
+	return retval;
+}
+EXPORT_SYMBOL_GPL(handle_dumb_demux_irq);

This should go into the new file as well, so it gets compiled out when
not enabled.

+static void irq_dumb_demux_mask(struct irq_data *d)
+{
+	struct irq_chip_dumb_demux *demux = irq_data_get_irq_chip_data(d);
+
+	clear_bit(d->hwirq, demux->unmasked);
+}
+
+static void irq_dumb_demux_unmask(struct irq_data *d)
+{
+	struct irq_chip_dumb_demux *demux = irq_data_get_irq_chip_data(d);
+
+	set_bit(d->hwirq, demux->unmasked);
+}

So this needs the handling of enabling/disabling the source irq.

+static struct irq_chip irq_dumb_demux_chip = {
+	.name = "dumb-demux-irq",
+	.irq_mask = irq_dumb_demux_mask,
+	.irq_unmask = irq_dumb_demux_unmask,

+	.name		= "dumb-demux-irq",
+	.irq_mask	= irq_dumb_demux_mask,
+	.irq_unmask	= irq_dumb_demux_unmask,

Makes it simpler to read.

+struct irq_domain_ops irq_dumb_demux_domain_ops = {
+	.map	= irq_map_dumb_demux_chip,
+	.xlate	= irq_domain_xlate_onecell,
+};
+EXPORT_SYMBOL(irq_dumb_demux_domain_ops);

SYMBOL_GPL please

Rest looks good.

Thanks,

	tglx