[RFC patch 00/20] Interrupt chip consolidation

[Thomas Gleixner]

On Tue, 19 Apr 2011, Lars-Peter Clausen wrote:
> On 04/16/2011 11:14 PM, Thomas Gleixner wrote:
> > [...]
> >
> > That converts 18 irq_chips and removes at least one duplicated VIC
> > implementation.
> >
> > Please have a look and check also the not yet converted chips whether
> > they could make use of such an generic implementation. We better have
> > some oddball callback functions in the generic code than ten slightly
> > different instances of them all over the place.
> >
> 
> I've adopted JZ4740 platform which is MIPS based SoC to the generic_irq_chip
> and the diffstat looks ok:
> 
>  arch/mips/jz4740/gpio.c  |  116 +++++++++++++++-------------------------------
>  arch/mips/jz4740/irq.c   |   95 +++++++++++++++----------------------
>  arch/mips/jz4740/pm.c    |    2 -
>  drivers/mfd/jz4740-adc.c |   73 +++++++----------------------
>  4 files changed, 94 insertions(+), 192 deletions(-)

Nice!
 
> I've also noticed that all my chained demuxer handlers follow a similar scheme
> and a quick grep for generic_handle_irq revealed that quite a few other
> implementations also follow a similar scheme as well.
> 
> Something along the lines of ...
> 
> void irq_gc_chained_demux_handler(unsigned int irq, struct irq_desc *desc)
> {
> 	struct irq_chip_generic *gc = irq_desc_get_handler_data(desc);
> 	struct irq_chip_type *ct = gc = irq_chip_generic_current_chip_type(gc);
> 	unsigned long pending = irq_reg_readl(ct->regs.pending);
> 
> 	pending = irq_reg_readl(ct->regs.pending) & gc->mask_cache;
> 
> 	for_each_set_bit (irq, &pending, gc->irq_cnt)
> 		generic_handle_irq(gc->irq_base + irq);
> }
> 
> ... could be used to replace those custom handlers in an irq_chip_generic based
> implementation.
> 
> With this the diffstat for JZ4740 looks even better:
>  4 files changed, 91 insertions(+), 232 deletions(-)
> 
> Unfortunately it doesn't completely fit into the current irq_chip_generic
> implementation. For one there is no irq_chip_generic_current_chip_type, but I
> guess that could be implementing by adding a field to irq_chip_generic pointing
> to the current chip type. On the other hand I'm not sure if it is necessary to

No, you can get the current chip from irq_data.chip which always has a
pointer to the current active one. container_of will give you the
generic chip.

> have different pending registers for different chip types of the same
> irq_chip_generic.
> 
> Another issue is that while the gpio unit on the JZ4740 supports different
> trigger modes it only supports either rising or falling edge at one time. So
> since it doesn't makes sense to implement switching between those two in a
> driver triggering in both edges is emulated by the irq chip.

That's what about 5 dozen other irq chips do as well.

> Also related to gpio irq chips is the lockdep class issue.
> Would it make sense to add a lockdep class parameter to irq_setup_generic_chip
> or is this something better put into a separate function along the lines of.
> 
> void irq_generic_chip_set_lockclass(struct irq_generic_chip *gc,
> 	struct lock_class_key *lockdep_class)
> {
> 	unsigned int irq;
> 	for (irq = 0; irq < gc->irq_cnt; irq++)
> 		irq_set_lockdep_class(gc->irq_bas + irq, lockdep_class);
> }

Probably yes.

Thanks,

	tglx