Re: [PATCH WIP 6/6] xen/arm: enable evtchn irqs

From: Konrad Rzeszutek Wilk
Date: Mon Jul 16 2012 - 11:05:53 EST


On Fri, Jul 13, 2012 at 06:14:33PM +0100, Stefano Stabellini wrote:
> On Mon, 9 Jul 2012, Konrad Rzeszutek Wilk wrote:
> > On Fri, Jun 22, 2012 at 05:14:45PM +0100, Stefano Stabellini wrote:
> > > On ARM irqs are not enabled by default:
> >
> > Which IRQs? Xen IRQs? Linux IRQs?
>
> Linux IRQs
>
>
> > > - call enable_percpu_irq for IRQ_EVTCHN_CALLBACK;
> >
> > Why do we want to do that?
>
> drivers are supposed to call enable_irq after request_irq, however on
> x86 we could get away without it because Linux irqs are enabled by
> default (see below)
>
>
> > > - set the IRQF_VALID flag for the other irqs bound to evtchns. It causes
> > > IRQ_NOAUTOEN to be set and as a consequence irq_unmask is going to be
> > > called when a xenbus driver calls request_irq.
> >
> > Can you explain in more details why we need that?
>
> If _IRQ_NOAUTOEN is set, irq_settings_can_autoenable returns false and
> __setup_irq doesn't call irq_startup.
>
> IRQ_NOAUTOEN is set by default by set_irq_flags on ARM, but not on x86.

OK, please include those questions/answers in the git commit and
repost.

>
>
>
> > > Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
> > > ---
> > > drivers/xen/events.c | 3 +++
> > > 1 files changed, 3 insertions(+), 0 deletions(-)
> > >
> > > diff --git a/drivers/xen/events.c b/drivers/xen/events.c
> > > index 0132505..ca92755 100644
> > > --- a/drivers/xen/events.c
> > > +++ b/drivers/xen/events.c
> > > @@ -53,6 +53,7 @@
> > > #include <xen/interface/hvm/params.h>
> > > #include <xen/interface/physdev.h>
> > > #include <xen/interface/sched.h>
> > > +#include <asm/hw_irq.h>
> > >
> > > /*
> > > * This lock protects updates to the following mapping and reference-count
> > > @@ -827,6 +828,7 @@ int bind_evtchn_to_irq(unsigned int evtchn)
> > >
> > > xen_irq_info_evtchn_init(irq, evtchn);
> > > }
> > > + set_irq_flags(irq, IRQF_VALID);
> > >
> > > out:
> > > mutex_unlock(&irq_mapping_update_lock);
> > > @@ -1751,6 +1753,7 @@ int __init xen_init_IRQ_arm(void)
> > > if (rc) {
> > > printk(KERN_ERR "Error requesting IRQ %d\n", IRQ_EVTCHN_CALLBACK);
> > > }
> > > + enable_percpu_irq(IRQ_EVTCHN_CALLBACK, 0);
> > > return rc;
> > > }
> > > core_initcall(xen_init_IRQ_arm);
> > > --
> > > 1.7.2.5
> > >
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