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

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Message-ID: <20120709144005.GA12102@phenom.dumpdata.com>
Date:	Mon, 9 Jul 2012 10:40:05 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com,
	Ian.Campbell@...rix.com, tim@....org
Subject: Re: [PATCH WIP 6/6] xen/arm: enable evtchn irqs

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?
> 
> - call enable_percpu_irq for IRQ_EVTCHN_CALLBACK;

Why do we want to do that?

> 
> - 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?
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> ---
>  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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