From: David Howells <dhowells@redhat.com>
To: Jeff Garzik <jgarzik@mandrakesoft.com>
Cc: David Howells <dhowells@redhat.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC] I/O Access Abstractions
Date: Tue, 03 Jul 2001 09:07:02 +0100 [thread overview]
Message-ID: <3938.994147622@warthog.cambridge.redhat.com> (raw)
In-Reply-To: Message from Jeff Garzik <jgarzik@mandrakesoft.com> of "Tue, 03 Jul 2001 04:00:09 EDT." <3B417B89.6FE1D06A@mandrakesoft.com>
> David Howells wrote:
> > For example, one board I've got doesn't allow you to do a straight
> > memory-mapped I/O access to your PCI device directly, but have to
> > reposition a window in the CPU's memory space over part of the PCI memory
> > space first, and then hold a spinlock whilst you do it.
>
> Yuck. Does that wind up making MMIO slower than PIO, on this board?
The mapping is not symmetrical (things on the PCI bus can see more of the CPU
bus at any one time than the reverse, so DMA isn't a problem), and at the
moment I have only one device on it that I'm actually using (the ethernet
chipset).
David
next prev parent reply other threads:[~2001-07-03 8:07 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-06-28 13:13 [RFC] I/O Access Abstractions David Howells
2001-06-28 13:32 ` Alan Cox
2001-06-28 13:55 ` David Woodhouse
2001-06-28 16:02 ` Jes Sorensen
2001-06-29 8:31 ` David Howells
2001-06-29 21:02 ` Jes Sorensen
2001-07-02 14:22 ` David Woodhouse
2001-07-02 15:57 ` David Howells
2001-07-02 16:17 ` David Woodhouse
2001-07-02 16:20 ` Alan Cox
2001-07-02 16:41 ` David Woodhouse
2001-07-02 16:56 ` Alan Cox
2001-07-02 18:22 ` Russell King
2001-07-02 18:26 ` Jeff Garzik
2001-07-02 20:10 ` Alan Cox
2001-07-02 22:08 ` Benjamin Herrenschmidt
2001-07-02 22:15 ` Alan Cox
2001-07-02 23:54 ` Benjamin Herrenschmidt
2001-07-03 12:02 ` Alan Cox
2001-07-03 14:38 ` Benjamin Herrenschmidt
2001-07-03 2:06 ` Jeff Garzik
2001-07-03 8:38 ` David Howells
2001-07-07 11:27 ` Geert Uytterhoeven
2001-07-03 8:15 ` David Howells
2001-07-03 8:22 ` Jeff Garzik
2001-07-03 8:31 ` Jeff Garzik
2001-07-03 9:00 ` David Howells
2001-07-03 9:29 ` Jeff Garzik
2001-07-02 22:10 ` Benjamin Herrenschmidt
2001-07-03 8:04 ` David Howells
2001-07-03 7:55 ` David Howells
2001-07-03 8:00 ` Jeff Garzik
2001-07-03 8:07 ` David Howells [this message]
2001-07-03 11:53 ` Alan Cox
2001-07-07 11:26 ` Geert Uytterhoeven
[not found] <20010702191129.A29246@flint.arm.linux.org.uk>
2001-07-03 8:12 ` David Howells
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