From: Arnd Bergmann <arnd@arndb.de>
To: Michal Simek <monstr@monstr.eu>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Grant Likely <grant.likely@secretlab.ca>,
Alexey Brodkin <Alexey.Brodkin@synopsys.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Vineet Gupta <Vineet.Gupta1@synopsys.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
dahinds@users.sourceforge.net
Subject: Re: [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be)
Date: Tue, 12 Feb 2013 13:55:25 +0000 [thread overview]
Message-ID: <201302121355.25762.arnd@arndb.de> (raw)
In-Reply-To: <CAHTX3dKn7iwbHyOnpJ4XiNbK766oqrJW06kH7XrAW2TJtOhehA@mail.gmail.com>
On Tuesday 12 February 2013, Michal Simek wrote:
> ok but still there should be well defined how to do it. Let's say
> generic Kconfig option.
You cannot solve it in a generic way, since every device has different
needs. In a single SoC, you may have one device that only ever exists
with little-endian I/O, one that is always wired the same way as the
CPU, one that always swaps endianess and one that exists in two
variants but you know which one you have at compile time.
> Or maybe there is also third option to modified code to use proper writes.
You mean run-time code patching? That is seriously wrong here. As Ben
explained, MMIO is slow by definition, so if you add five cycles for
an indirect function call on every MMIO read, that will not even
be noticeable in the 20µs latency that the read has on the bus.
Arnd
next prev parent reply other threads:[~2013-02-12 13:55 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-29 16:02 [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be) Alexey Brodkin
2013-01-29 16:27 ` Arnd Bergmann
2013-01-30 11:03 ` Alexey Brodkin
2013-01-30 11:13 ` Michal Simek
2013-01-30 12:10 ` Vineet Gupta
2013-01-30 12:31 ` Michal Simek
2013-01-30 14:36 ` Arnd Bergmann
2013-02-04 9:26 ` Michal Simek
2013-02-04 17:24 ` Arnd Bergmann
2013-02-05 2:29 ` Benjamin Herrenschmidt
2013-02-05 10:54 ` Michal Simek
2013-02-05 12:09 ` Vineet Gupta
2013-02-05 12:29 ` Benjamin Herrenschmidt
2013-02-05 12:19 ` Benjamin Herrenschmidt
2013-02-05 12:38 ` Michal Simek
2013-02-05 14:03 ` Alexey Brodkin
2013-02-05 15:12 ` Arnd Bergmann
2013-02-05 21:01 ` Benjamin Herrenschmidt
2013-02-06 10:03 ` Grant Likely
2013-02-06 16:20 ` Arnd Bergmann
2013-02-06 16:21 ` Michal Simek
2013-02-07 0:34 ` Arnd Bergmann
2013-02-06 17:40 ` Michal Simek
2013-02-06 19:51 ` Geert Uytterhoeven
2013-02-07 7:23 ` Michal Simek
2013-02-07 7:38 ` Geert Uytterhoeven
2013-02-07 8:01 ` Michal Simek
2013-02-07 8:20 ` Geert Uytterhoeven
2013-02-07 8:33 ` Arnd Bergmann
2013-02-07 14:19 ` Michal Simek
2013-02-07 23:12 ` Arnd Bergmann
2013-02-11 10:38 ` Michal Simek
2013-02-11 15:26 ` Arnd Bergmann
2013-02-11 15:36 ` Michal Simek
2013-02-11 15:43 ` Arnd Bergmann
2013-02-11 15:57 ` Michal Simek
2013-02-11 16:08 ` Arnd Bergmann
2013-02-12 0:29 ` Benjamin Herrenschmidt
2013-02-12 11:29 ` Arnd Bergmann
2013-02-12 10:11 ` Michal Simek
2013-02-12 11:26 ` Arnd Bergmann
2013-02-12 12:14 ` Michal Simek
2013-02-12 13:55 ` Arnd Bergmann [this message]
2013-02-12 12:30 ` Benjamin Herrenschmidt
2013-02-12 0:25 ` Benjamin Herrenschmidt
2013-02-12 10:03 ` Michal Simek
2013-02-05 21:00 ` Benjamin Herrenschmidt
2013-02-05 21:25 ` Alexey Brodkin
2013-02-05 23:07 ` Benjamin Herrenschmidt
2013-02-06 10:14 ` Grant Likely
2013-02-06 16:27 ` Arnd Bergmann
2013-02-06 21:35 ` Benjamin Herrenschmidt
2013-02-07 12:09 ` Alexey Brodkin
2013-02-07 12:20 ` Benjamin Herrenschmidt
2013-02-07 12:23 ` Benjamin Herrenschmidt
2013-02-07 14:31 ` Michal Simek
2013-02-07 14:35 ` Alexey Brodkin
2013-02-07 14:39 ` Grant Likely
2013-02-07 14:51 ` Grant Likely
2013-02-07 15:12 ` Alexey Brodkin
2013-02-07 15:23 ` Grant Likely
2013-02-07 15:28 ` Alexey Brodkin
2013-02-07 16:44 ` Grant Likely
2013-02-07 16:56 ` Alexey Brodkin
2013-02-07 17:16 ` Grant Likely
2013-02-07 17:22 ` Alexey Brodkin
2013-02-08 7:45 ` Grant Likely
2013-02-07 21:18 ` Benjamin Herrenschmidt
2013-02-07 21:15 ` Benjamin Herrenschmidt
2013-02-07 23:05 ` Arnd Bergmann
2013-02-08 6:19 ` Geert Uytterhoeven
2013-02-08 7:14 ` Grant Likely
2013-02-07 21:09 ` Benjamin Herrenschmidt
2013-02-12 17:02 ` Michal Simek
2013-02-12 17:25 ` Arnd Bergmann
2013-03-21 17:01 ` Alexey Brodkin
2013-06-19 8:56 ` xsysace driver support on arches other than PPC/Microblaze Alexey Brodkin
2013-06-19 9:09 ` Alexey Brodkin
2013-06-19 12:13 ` Andy Shevchenko
2013-06-19 12:56 ` Alexey Brodkin
2013-06-19 14:51 ` Arnd Bergmann
2013-02-07 21:06 ` [PATCH] drivers/block/xsysace - replace in(out)_8/in(out)_be16/in(out)_le16 with generic iowrite(read)8/16(be) Benjamin Herrenschmidt
2013-02-05 23:03 ` Arnd Bergmann
2013-02-06 8:59 ` Geert Uytterhoeven
2013-02-06 16:18 ` Arnd Bergmann
2013-02-05 10:45 ` Michal Simek
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