From: Sergei Shtylyov <sshtylyov@ru•mvista.com>
To: Linas Vepstas <linas@austin•ibm.com>
Cc: linuxppc-dev@ozlabs•org, paulus@samba•org,
Stephen Rothwell <sfr@canb•auug.org.au>
Subject: Re: [PATCH]: powerpc documentation: Clarify why twi appears in the i/o macros.
Date: Wed, 06 Dec 2006 21:39:00 +0300 [thread overview]
Message-ID: <45770E44.30000@ru.mvista.com> (raw)
In-Reply-To: <20061206182922.GA17931@austin.ibm.com>
Hello.
Linas Vepstas wrote:
> Paul,
> Please apply. This atch resulted from an email discussion
> back in Sept.
> --linas
> Clarify why twi appears in the i/o macros.
> Signed-off-by: Linas Vepstas <linas@austin•ibm.com>
> Signed-off-by: Segher Boessenkool <segher@kernel•crashing.org>
>
> ----
> include/asm-powerpc/io.h | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> Index: linux-2.6.19-git7/include/asm-powerpc/io.h
> ===================================================================
> --- linux-2.6.19-git7.orig/include/asm-powerpc/io.h 2006-12-05 17:11:02.000000000 -0600
> +++ linux-2.6.19-git7/include/asm-powerpc/io.h 2006-12-06 11:48:43.000000000 -0600
> @@ -78,6 +78,17 @@ extern unsigned long pci_dram_offset;
> * Note: I might drop the _ns suffix on the stream operations soon as it is
> * simply normal for stream operations to not swap in the first place.
> *
> + * Read operations have additional twi & isync to make sure the read
> + * is actually performed (i.e. the data has come back) before we start
> + * executing any following instructions.
> + *
> + * A data-dependent branch followed by an isync ensures that no
> + * instructions after the isync in program order will be
> + * (speculatively) executed before the isync has completed, and
> + * the isync won't complete until the branch is resolved. The
> + * the load that the twi depends on has to complete before
A minor type here -- double "the".
> + * anything else is executed; in particular, it's a barrier to
> + * keep MMIO reads ordered before main-storage accesses.
> */
>
> #ifdef CONFIG_PPC64
WBR, Sergei
next prev parent reply other threads:[~2006-12-06 18:37 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-06 18:29 [PATCH]: powerpc documentation: Clarify why twi appears in the i/o macros Linas Vepstas
2006-12-06 18:39 ` Sergei Shtylyov [this message]
2006-12-06 19:45 ` Linas Vepstas
[not found] ` <45772700.2080708@ru.mvista.com>
2006-12-06 22:22 ` Linas Vepstas
2006-12-08 2:58 ` Paul Mackerras
2006-12-08 21:54 ` Segher Boessenkool
2006-12-09 0:11 ` Linas Vepstas
2006-12-09 0:19 ` Paul Mackerras
2006-12-09 1:21 ` Linas Vepstas
2006-12-09 9:32 ` Segher Boessenkool
2006-12-11 2:37 ` Paul Mackerras
2006-12-11 16:37 ` Segher Boessenkool
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