From: Arnd Bergmann <arnd@arndb.de>
To: Chris Metcalf <cmetcalf@tilera.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/6] arch/tile: support MMIO-based readb/writeb etc.
Date: Mon, 9 Apr 2012 13:24:33 +0000 [thread overview]
Message-ID: <201204091324.34288.arnd@arndb.de> (raw)
In-Reply-To: <201204062101.q36L1tuT011403@farm-0027.internal.tilera.com>
On Friday 06 April 2012, Chris Metcalf wrote:
> Add support for MMIO read/write on tilegx to support GXIO IORPC access.
> Similar to the asm-generic version, but we include memory fences on
> the writes to be conservative.
>
> Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
It's usually better to use inline assembly here, to guarantee that
the compiler does not split an access into multiple byte sized
accesses as it might sometimes do if a register data structure
is marged "packed". The "volatile" guarantees that the access
does not go beyond a single word, but it does not guarantee that
it's atomic.
I don't think you need the fences after the write because PCI MMIO
writes are posted anyway (only PIO is non-posted), but you might need
some kind of barrier on the read to prevent a scenario where an MMIO
read tells you that a DMA has completed, but the CPU (or the compiler)
has scheduled the read of that data ahead of the MMIO read.
Arnd
next prev parent reply other threads:[~2012-04-09 13:24 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-04 20:39 [PATCH 0/6] arch/tile: provide tilegx networking support Chris Metcalf
2012-04-04 20:39 ` [PATCH 1/6] arch/tile: introduce GXIO IORPC framework for tilegx Chris Metcalf
2012-04-04 20:58 ` [PATCH 4/6] arch/tile: common DMA code for the GXIO IORPC subsystem Chris Metcalf
2012-04-06 17:41 ` [PATCH 2/6] arch/tile: fix set_pte() to properly handle kernel MMIO mappings Chris Metcalf
2012-04-06 17:52 ` [PATCH 3/6] arch/tile: support MMIO-based readb/writeb etc Chris Metcalf
2012-04-09 13:24 ` Arnd Bergmann [this message]
2012-04-09 20:53 ` Chris Metcalf
2012-04-06 20:38 ` [PATCH 5/6] arch/tile: provide kernel support for the tilegx mPIPE shim Chris Metcalf
2012-04-09 13:34 ` Arnd Bergmann
2012-04-09 21:04 ` Chris Metcalf
2012-04-06 20:42 ` [PATCH 6/6] tilegx network driver: initial support Chris Metcalf
2012-04-09 13:49 ` Arnd Bergmann
2012-04-09 21:30 ` Chris Metcalf
2012-04-10 10:42 ` Arnd Bergmann
2012-04-12 23:23 ` Chris Metcalf
2012-04-13 10:34 ` Arnd Bergmann
2012-04-28 22:07 ` Chris Metcalf
2012-04-04 20:39 ` [PATCH v2 0/6] arch/tile: networking support for tilegx Chris Metcalf
2012-04-04 20:39 ` [PATCH v2 1/6] arch/tile: introduce GXIO IORPC framework " Chris Metcalf
2012-04-04 20:58 ` [PATCH v2 3/6] arch/tile: common DMA code for the GXIO IORPC subsystem Chris Metcalf
2012-04-06 17:52 ` [PATCH v2 2/6] arch/tile: support MMIO-based readb/writeb etc Chris Metcalf
2012-04-06 20:38 ` [PATCH v2 4/6] arch/tile: provide kernel support for the tilegx mPIPE shim Chris Metcalf
2012-04-06 20:42 ` [PATCH v2 6/6] tilegx network driver: initial support Chris Metcalf
2012-04-30 14:35 ` Arnd Bergmann
2001-09-17 4:00 ` [PATCH v3] " Chris Metcalf
2012-05-03 5:41 ` David Miller
2012-05-03 15:45 ` Chris Metcalf
2012-05-03 17:07 ` David Miller
2012-05-03 17:25 ` Chris Metcalf
2012-05-03 16:41 ` [PATCH v4] " Chris Metcalf
2012-05-04 6:42 ` David Miller
2012-05-09 10:42 ` [PATCH v5] " Chris Metcalf
2012-05-11 13:54 ` Ben Hutchings
2012-05-20 4:42 ` [PATCH v6] " Chris Metcalf
2012-05-20 20:55 ` David Miller
2012-05-23 20:42 ` [PATCH v7] " Chris Metcalf
2012-05-24 4:31 ` David Miller
2012-05-25 14:42 ` [PATCH v8] " Chris Metcalf
2012-06-04 20:12 ` [PATCH v9] " Chris Metcalf
2012-06-06 16:41 ` David Miller
2012-06-06 17:31 ` Eric Dumazet
2012-06-06 17:40 ` Eric Dumazet
2012-06-06 18:36 ` Chris Metcalf
2012-06-06 18:54 ` David Miller
2001-09-17 4:00 ` [PATCH v10] " Chris Metcalf
2012-04-06 20:42 ` Chris Metcalf
2012-06-07 20:39 ` David Miller
2012-06-07 20:44 ` Chris Metcalf
2012-06-07 20:47 ` Chris Metcalf
2012-06-07 20:50 ` Ben Hutchings
2012-06-07 20:52 ` Joe Perches
2012-06-07 20:45 ` Chris Metcalf
2012-06-12 0:03 ` David Miller
2012-06-12 13:14 ` Chris Metcalf
2012-06-06 18:10 ` [PATCH v9] " Eric Dumazet
2012-06-06 18:17 ` David Miller
2012-06-06 18:19 ` Ben Hutchings
2012-05-20 16:35 ` [PATCH v5] " Chris Metcalf
2012-04-28 19:41 ` [PATCH v2 5/6] arch/tile: break out the "csum a long" function to <asm/checksum.h> Chris Metcalf
2012-04-29 11:15 ` [PATCH 6/6] tilegx network driver: initial support Arnd Bergmann
2012-04-15 23:06 ` Chris Metcalf
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