From: Hitoshi Mitake <h.mitake@gmail.com>
To: "H. Peter Anvin" <hpa@linux.intel.com>
Cc: James Bottomley <jbottomley@parallels.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
Matthew Wilcox <matthew.r.wilcox@intel.com>,
Roland Dreier <roland@purestorage.com>,
Andrew Morton <akpm@linux-foundation.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] NVMe: Fix compilation on architecturs without readq/writeq
Date: Sun, 5 Feb 2012 00:39:00 +0900 [thread overview]
Message-ID: <CAMO-S2joH0fwEyOOCSFGM+Lc=xgiarNxm3Rj9DgWJNeoRD+QRQ@mail.gmail.com> (raw)
In-Reply-To: <4F2AA642.1030400@linux.intel.com>
On Fri, Feb 3, 2012 at 00:05, H. Peter Anvin <hpa@linux.intel.com> wrote:
> On 02/01/2012 05:05 PM, James Bottomley wrote:
>>
>>
>> Incidentally, the last time this came up was with mpt fusion: for a
>> write to a 64 bit register, it didn't care about order, but it did care
>> about interleaving as in if you write one half of a 64 bit register and
>> then write to another register, the 64 bit register effectively gets
>> written with zeros in the part you didn't write to, so we had to put a
>> spin lock in the open coded writeb/w/l/q() to make sure the card didn't
>> get interleaved writes.
>>
>
> There are always going to be hardware which have specific needs, and for
> those open-coding makes sense, but the littleendian/bigendian pair is going
> to cover ~90% of users and make sense to can.
>
> I worked myself on a driver (which sadly never shipped) which had an WC
> window and a UC window... the final write in a series had a completion bit
> in it and would go to the UC window after setting up a whole chunk of
> operations in the WC window (writing UC memory flushes WC memory ahead of
> it.)
>
> Thus, the two-part breakdown of writeq() to the UC window had to write the
> low half to the WC window instead. This is clearly not generic.
>
> -hpa
>
>
Because of my ignorant, I don't know the words "UC window" and "WC window"
in this context. Could you teach me?
--
Hitoshi Mitake
h.mitake@gmail.com
next prev parent reply other threads:[~2012-02-04 15:39 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-20 1:01 [PATCH] NVMe: Fix compilation on architecturs without readq/writeq Matthew Wilcox
2012-01-20 1:21 ` Linus Torvalds
2012-01-20 17:43 ` Wilcox, Matthew R
2012-01-21 8:28 ` Ingo Molnar
2012-01-21 15:54 ` Hitoshi Mitake
2012-01-21 16:58 ` Ingo Molnar
2012-01-23 16:05 ` Hitoshi Mitake
2012-01-23 16:57 ` Linus Torvalds
2012-01-23 23:04 ` H. Peter Anvin
2012-01-29 8:02 ` Hitoshi Mitake
2012-01-31 3:03 ` Linus Torvalds
2012-01-31 3:05 ` Linus Torvalds
2012-02-04 15:25 ` Hitoshi Mitake
2012-01-31 11:58 ` Alan Cox
2012-01-31 12:09 ` Ingo Molnar
2012-01-31 12:18 ` Alan Cox
2012-01-31 12:23 ` Ingo Molnar
2012-02-01 23:35 ` Linus Torvalds
2012-02-02 1:05 ` James Bottomley
2012-02-02 1:15 ` Linus Torvalds
2012-02-02 15:05 ` H. Peter Anvin
2012-02-04 15:39 ` Hitoshi Mitake [this message]
2012-02-05 6:53 ` Geert Uytterhoeven
2012-02-05 7:01 ` Hitoshi Mitake
2012-02-04 15:34 ` Hitoshi Mitake
2012-02-07 2:48 ` Hitoshi Mitake
2012-02-04 15:24 ` Hitoshi Mitake
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