From: Peter Korsgaard <jacmet@sunsite•dk>
To: Benjamin Herrenschmidt <benh@kernel•crashing.org>
Cc: sfr@canb•auug.org.au, linuxppc-dev@ozlabs•org
Subject: Re: Recently removed io accessors
Date: Fri, 13 Oct 2006 08:56:34 +0200 [thread overview]
Message-ID: <87iriovh3x.fsf@sleipner.barco.com> (raw)
In-Reply-To: <1160697861.4792.177.camel@localhost.localdomain> (Benjamin Herrenschmidt's message of "Fri, 13 Oct 2006 10:04:21 +1000")
>>>>> "BH" == Benjamin Herrenschmidt <benh@kernel•crashing.org> writes:
Hi,
>> Any chance of getting them back or should I implement a (slower)
>> loop myself before submitting the patch?
BH> Well, a "packet buffer" should have no endian. When streaming in
BH> our out a fifo, you basically stream bytes that happen to come out
BH> 2 at a time. So unless somebody wired the hardware backward, you
BH> should do no swapping when using the fifo.
I agree in principle, but the issue gets complicated by the fact that
the chip works in chunks of 32bit, but the 911{5..7} chips only have a
16bit interface to lower costs, and that the chip has a builtin endian
swap feature (which works for all direct registers, but apparently not
for the packet buffers).
The memory controller automatically translates a 32bit access to two
16 bit accesses.
You could be right that the hw people screwed something up, but that
doesn't help much once there's units in the field :/
--
Bye, Peter Korsgaard
next prev parent reply other threads:[~2006-10-13 6:56 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-10-12 15:44 Recently removed io accessors Peter Korsgaard
2006-10-13 0:04 ` Benjamin Herrenschmidt
2006-10-13 6:56 ` Peter Korsgaard [this message]
2006-10-13 7:31 ` Benjamin Herrenschmidt
2006-10-13 8:43 ` Peter Korsgaard
2006-10-13 9:30 ` Benjamin Herrenschmidt
2006-10-13 9:55 ` Peter Korsgaard
2006-10-13 12:18 ` Benjamin Herrenschmidt
2006-10-13 12:38 ` Peter Korsgaard
2006-10-13 23:20 ` Paul Mackerras
2006-10-14 11:57 ` Peter Korsgaard
2006-10-16 16:51 ` Linas Vepstas
2006-10-16 18:54 ` Peter Korsgaard
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