From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
Cc: linuxppc-dev@lists.ozlabs.org,
Purcareata Bogdan <b43198@freescale.com>,
linux-kernel@vger.kernel.org, Andreas Mohr <andi@lisas.de>
Subject: Re: [RFC] PPC: MPIC: necessary readback after EOI?
Date: Wed, 07 Jan 2015 15:44:36 +0100 [thread overview]
Message-ID: <1420641876.5830.32.camel@kernel.crashing.org> (raw)
In-Reply-To: <1420481454.4961.16.camel@freescale.com>
On Mon, 2015-01-05 at 12:10 -0600, Scott Wood wrote:
> It would have been nice if a code comment explained why it was doing the
> readback... I don't see any particular need to wait for EOI completion
> here (unlike when masking).
The EOI is what causes the MPIC to drop it's EE output to the CPU, if the
EOI is processed too slowly & asynchronously (posted write + 33Mhz MPIC)
we observe cases of spurrious interrupts. We had some macs basically getting
a spurrious irq for every MPIC interrupts...
Cheers,
Ben.
WARNING: multiple messages have this Message-ID (diff)
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Scott Wood <scottwood@freescale.com>
Cc: Andreas Mohr <andi@lisas.de>,
Purcareata Bogdan <b43198@freescale.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC] PPC: MPIC: necessary readback after EOI?
Date: Wed, 07 Jan 2015 15:44:36 +0100 [thread overview]
Message-ID: <1420641876.5830.32.camel@kernel.crashing.org> (raw)
In-Reply-To: <1420481454.4961.16.camel@freescale.com>
On Mon, 2015-01-05 at 12:10 -0600, Scott Wood wrote:
> It would have been nice if a code comment explained why it was doing the
> readback... I don't see any particular need to wait for EOI completion
> here (unlike when masking).
The EOI is what causes the MPIC to drop it's EE output to the CPU, if the
EOI is processed too slowly & asynchronously (posted write + 33Mhz MPIC)
we observe cases of spurrious interrupts. We had some macs basically getting
a spurrious irq for every MPIC interrupts...
Cheers,
Ben.
next prev parent reply other threads:[~2015-01-07 15:44 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-05 14:14 [RFC] PPC: MPIC: necessary readback after EOI? Purcareata Bogdan
2015-01-05 14:14 ` Purcareata Bogdan
2015-01-05 17:46 ` Andreas Mohr
2015-01-05 17:46 ` Andreas Mohr
2015-01-05 18:10 ` Scott Wood
2015-01-05 18:10 ` Scott Wood
2015-01-05 18:43 ` Andreas Mohr
2015-01-05 18:43 ` Andreas Mohr
2015-01-07 2:56 ` Scott Wood
2015-01-07 2:56 ` Scott Wood
2015-01-07 14:44 ` Benjamin Herrenschmidt [this message]
2015-01-07 14:44 ` Benjamin Herrenschmidt
2015-01-07 17:04 ` Scott Wood
2015-01-07 17:04 ` Scott Wood
2015-01-08 19:17 ` Benjamin Herrenschmidt
2015-01-08 19:17 ` Benjamin Herrenschmidt
2015-01-07 14:43 ` Benjamin Herrenschmidt
2015-01-07 14:43 ` Benjamin Herrenschmidt
2015-01-07 14:40 ` Benjamin Herrenschmidt
2015-01-08 0:49 ` Segher Boessenkool
2015-01-08 0:49 ` Segher Boessenkool
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