From: Scott Wood <scottwood@freescale•com>
To: Kumar Gala <galak@kernel•crashing.org>
Cc: linuxppc-dev@ozlabs•org, Paul Mackerras <paulus@samba•org>
Subject: Re: [PATCH] qe_ic: Do a sync when masking interrupts.
Date: Mon, 23 Oct 2006 13:22:57 -0500 [thread overview]
Message-ID: <453D0881.500@freescale.com> (raw)
In-Reply-To: <E8190CD2-1898-473E-812A-AE2CBD85D73A@kernel.crashing.org>
Kumar Gala wrote:
>
> On Oct 23, 2006, at 10:19 AM, Scott Wood wrote:
>> Possibly -- but the only problem on the rare occasions where the timing
>> is not fortuitous is a spurious interrupt; the only reason the sync
>> needs to be there at all is to avoid the overhead of the extra interrupt
>> (and to avoid user complaints that they're getting "BAD" interrupts).
>
>
> Why wouldn't the read accomplish the same thing in a more robust way
> than the sync?
It would. However, it also adds a small amount of overhead to every QE
interrupt, and the only thing that that overhead buys is avoiding
possible but empirically very rare spurious interrupts; it'd cost more
than simply accepting that a spurious interrupt might happen once in a
great while.
Without any type of sync, spurious interrupts happen fairly regularly
(about 5-10% of legitimate interrupts), so adding the sync should be a
net gain over doing nothing.
If the consensus is that a read should be done anyway, I can resumbit
the patch that way; I just think it's overkill given that a 100%
guarantee isn't required for correctness.
-Scott
next prev parent reply other threads:[~2006-10-23 18:23 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-19 18:03 [PATCH] qe_ic: Do a sync when masking interrupts Scott Wood
2006-10-20 3:03 ` Li Yang-r58472
2006-10-23 3:59 ` Paul Mackerras
2006-10-23 9:35 ` Li Yang-r58472
2006-10-23 15:19 ` Scott Wood
2006-10-23 15:29 ` Scott Wood
2006-10-23 17:52 ` Kumar Gala
2006-10-23 18:22 ` Scott Wood [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-10-23 15:30 Michael R. Zucca
2006-10-23 16:49 ` Segher Boessenkool
2006-10-23 18:27 ` Scott Wood
2006-10-23 18:46 ` Segher Boessenkool
2006-10-24 7:17 ` Li Yang-r58472
2006-10-25 3:51 ` Benjamin Herrenschmidt
2006-10-25 4:47 ` Liu Dave-r63238
2006-10-23 18:53 Scott Wood
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