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From: Segher Boessenkool <segher@kernel.crashing.org>
To: benh@kernel.crashing.org
Cc: kvm-ppc-devel <kvm-ppc-devel@lists.sourceforge.net>,
	linuxppc-dev@ozlabs.org, Stefan Roese <sr@denx.de>,
	Hollis Blanchard <hollisb@us.ibm.com>
Subject: Re: [kvm-ppc-devel] Bamboo PCI interrupt issues
Date: Tue, 04 Mar 2008 20:39:29 +0000	[thread overview]
Message-ID: <9eeb7e8e1acf8a9217a5121fe4ec69d8@kernel.crashing.org> (raw)
In-Reply-To: <1204612384.21545.50.camel@pasglop>

>> Using '8' is correct. PCI interrupts are *always* level sensitive and
>> active
>> low.
>
> Unless you use one of those strange bridges that stick not gates on the
> PCI IRQ inputs :-) But I don't think that's the case on the 440EP.

More generally, the target interrupt descriptors (sense values, in
particular) in a device tree interrupt map describe the interrupts as
seen on the target interrupt controller, *not* as seen on this (source)
interrupt domain.  This should be obvious, but since the source 
interrupt
descriptor for PCI doesn't have a sense value (it's always level low,
after all), it can be confusing.  Well, interrupts always are confusing 
:-)


Segher


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WARNING: multiple messages have this Message-ID (diff)
From: Segher Boessenkool <segher@kernel.crashing.org>
To: benh@kernel.crashing.org
Cc: kvm-ppc-devel <kvm-ppc-devel@lists.sourceforge.net>,
	linuxppc-dev@ozlabs.org, Stefan Roese <sr@denx.de>,
	Hollis Blanchard <hollisb@us.ibm.com>
Subject: Re: Bamboo PCI interrupt issues
Date: Tue, 4 Mar 2008 21:39:29 +0100	[thread overview]
Message-ID: <9eeb7e8e1acf8a9217a5121fe4ec69d8@kernel.crashing.org> (raw)
In-Reply-To: <1204612384.21545.50.camel@pasglop>

>> Using '8' is correct. PCI interrupts are *always* level sensitive and
>> active
>> low.
>
> Unless you use one of those strange bridges that stick not gates on the
> PCI IRQ inputs :-) But I don't think that's the case on the 440EP.

More generally, the target interrupt descriptors (sense values, in
particular) in a device tree interrupt map describe the interrupts as
seen on the target interrupt controller, *not* as seen on this (source)
interrupt domain.  This should be obvious, but since the source 
interrupt
descriptor for PCI doesn't have a sense value (it's always level low,
after all), it can be confusing.  Well, interrupts always are confusing 
:-)


Segher

  reply	other threads:[~2008-03-04 20:39 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-04  0:02 [kvm-ppc-devel] Bamboo PCI interrupt issues Hollis Blanchard
2008-03-04  0:02 ` Hollis Blanchard
2008-03-04  0:59 ` [kvm-ppc-devel] " David Gibson
2008-03-04  0:59   ` David Gibson
2008-03-04  1:42   ` [kvm-ppc-devel] " Benjamin Herrenschmidt
2008-03-04  1:42     ` Benjamin Herrenschmidt
2008-03-04  1:53     ` [kvm-ppc-devel] " David Gibson
2008-03-04  1:53       ` David Gibson
2008-03-04  2:07       ` [kvm-ppc-devel] " Segher Boessenkool
2008-03-04  2:07         ` Segher Boessenkool
2008-03-04  2:15         ` [kvm-ppc-devel] " David Gibson
2008-03-04  2:15           ` David Gibson
2008-03-04  3:37 ` [kvm-ppc-devel] " Josh Boyer
2008-03-04  3:37   ` Josh Boyer
2008-03-04  6:15   ` [kvm-ppc-devel] " Stefan Roese
2008-03-04  6:15     ` Stefan Roese
2008-03-04  6:33     ` [kvm-ppc-devel] " Benjamin Herrenschmidt
2008-03-04  6:33       ` Benjamin Herrenschmidt
2008-03-04 20:39       ` Segher Boessenkool [this message]
2008-03-04 20:39         ` Segher Boessenkool
2008-03-04 20:41         ` [kvm-ppc-devel] " Benjamin Herrenschmidt
2008-03-04 20:41           ` Benjamin Herrenschmidt
2008-03-04 20:59           ` [kvm-ppc-devel] " Segher Boessenkool
2008-03-04 20:59             ` Segher Boessenkool
2008-03-04 21:01             ` [kvm-ppc-devel] " Benjamin Herrenschmidt
2008-03-04 21:01               ` Benjamin Herrenschmidt
2008-03-04  6:18   ` [kvm-ppc-devel] " Benjamin Herrenschmidt
2008-03-04  6:18     ` Benjamin Herrenschmidt

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