linux-kernel - Re: [PATCH] powerpc/mpic: Add DT option to skip readback after EOI

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Message-ID: <1421258312.4961.133.camel@freescale.com>
Date:	Wed, 14 Jan 2015 11:58:32 -0600
From:	Scott Wood <scottwood@...escale.com>
To:	Bogdan Purcareata <bogdan.purcareata@...escale.com>
CC:	<benh@...nel.crashing.org>, <linuxppc-dev@...ts.ozlabs.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] powerpc/mpic: Add DT option to skip readback after EOI

On Wed, 2015-01-14 at 11:57 +0000, Bogdan Purcareata wrote:
> The readback is necessary in order to handle PCI posted
> writes,

That is unclear.

>  or when the MPIC is handling interrupts in a loop
> (ppc_md.get_irq).

I'm questioning this one as well -- if reading WHOAMI is sufficient to
sync with the EOI, why wouldn't reading INTACK work as well?

>  Newer MPIC versions don't require this readback. Leave the option
> configurable using a device tree entry.
> 
> This saves a MMIO trap per interrupt.
> 
> Signed-off-by: Scott Wood <scottwood@...escale.com>
> Signed-off-by: Bogdan Purcareata <bogdan.purcareata@...escale.com>

You should note changes (e.g. with a [] note between signoffs) if it
differs from the original...

-Scott


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