Re: [PATCH v6 2/2] clocksource: add J-Core timer/clocksource driver

From: Marc Zyngier
Date: Wed Aug 24 2016 - 15:02:00 EST

On Wed, 24 Aug 2016 13:40:01 -0400
Rich Felker <dalias@xxxxxxxx> wrote:


> > IIUC, there is a problem with the interrupt controller where
the per irq
> > line are not working correctly. Is that correct ?
> I don't think that's a correct characterization. Rather the percpu
> infrastructure just means something completely different from what you
> would expect it to mean. It has nothing to do with the hardware but
> rather with kernel-internal choice of whether to do percpu devid
> mapping inside the irq infrastructure, and the choice at the
> irq-requester side of whether to do this is required to match the
> irqchip driver's choice. I explained this better in another email
> which I could dig up if necessary, but the essence is that
> request_percpu_irq is a misnamed and unusably broken API.

Or just one that simply doesn't fit your needs, because other
architectures have different semantics than the ones you take for

> > Regarding Marc Zyngier comments about the irq controller driver being
> > almost empty, I'm wondering if something in the irq controller driver
> > which shouldn't be added before submitting this timer driver with SMP
> > support (eg. irq domain ?).
> I don't think so. At most I could make the driver hard-code the percpu
> devid model for certain irqs, but that _does not reflect_ anything
> about the hardware. Rather it just reflects bad kernel internals. It

I'd appreciate it if instead of ranting about how broken the kernel is,
you'd submit a patch fixing it, since you seem to have spotted
something that we haven't in several years of using that code on a
couple of ARM-related platforms.


Jazz is not dead. It just smells funny.