From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Petr Vandrovec <vandrove@vc.cvut.cz>
Cc: Linus Torvalds <torvalds@osdl.org>,
Roland Dreier <roland@topspin.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Andrew Morton <akpm@osdl.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] ppc64: Fix __raw_* IO accessors
Date: Fri, 24 Sep 2004 08:23:25 +1000 [thread overview]
Message-ID: <1095978205.10865.30.camel@gaston> (raw)
In-Reply-To: <20040923152530.GA9377@vana.vc.cvut.cz>
On Fri, 2004-09-24 at 01:25, Petr Vandrovec wrote:
>
> Ok. Can somebody tell me what byte order should be used for framebuffer
> and for MMIO on PPC/PPC64 then? From cfb* it seems that framebuffer
> have to be in big-endian mode, and from Xorg code it seems that MMIO should
> be always in little-endian. Yes?
I don't know exactly what X.org does ...
In general, on a PCI bus, we expect MMIO to be little endian. Some cards
try to be "smart" and have an endian swap facility for MMIO (like nvidia,
and I think matrox) but I tend to consider that useless since it force us
to have different IO accessors or to add an "un-byteswap" macro. The PPC
is very good at doing byteswapped accesses with one instruction so it
isn't really a waste to do all MMIOs littel endian anyway.
For the framebuffer, it's common practice to have it in big endian format
(and using the proper byteswap register for the access bit depth)
Ben.
next prev parent reply other threads:[~2004-09-23 22:56 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-21 9:23 [PATCH] ppc64: Fix __raw_* IO accessors Benjamin Herrenschmidt
2004-09-21 10:05 ` Alan Cox
2004-09-21 11:41 ` Benjamin Herrenschmidt
2004-09-21 19:30 ` Roland Dreier
2004-09-21 19:41 ` Linus Torvalds
2004-09-21 20:55 ` Geert Uytterhoeven
2004-09-21 22:05 ` Roland Dreier
2004-09-21 22:16 ` Linus Torvalds
2004-09-22 1:34 ` Benjamin Herrenschmidt
2004-09-22 18:58 ` Petr Vandrovec
2004-09-23 0:49 ` Benjamin Herrenschmidt
2004-09-23 15:25 ` Petr Vandrovec
2004-09-23 20:26 ` [PATCH] matroxfb big-endian update (was Re: [PATCH] ppc64: Fix __raw_* IO accessors) Petr Vandrovec
2004-09-24 6:25 ` Benjamin Herrenschmidt
2004-09-24 9:53 ` Petr Vandrovec
2004-09-24 16:16 ` Kostas Georgiou
2004-09-25 1:40 ` Benjamin Herrenschmidt
2004-09-23 22:23 ` Benjamin Herrenschmidt [this message]
2004-09-22 2:15 ` [PATCH] ppc64: Fix __raw_* IO accessors Paul Mackerras
2004-09-22 7:36 ` Roland Dreier
2004-09-22 1:31 ` Benjamin Herrenschmidt
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