From: Jeff Garzik <jeff@garzik.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Luis R. Rodriguez" <mcgrof@gmail.com>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
linux-kernel <linux-kernel@vger.kernel.org>,
"John W. Linville" <linville@tuxdriver.com>,
linux-wireless <linux-wireless@vger.kernel.org>
Subject: Re: [PATCH] Clarify pci_iomap() usage for MMIO-only devices
Date: Tue, 18 Sep 2007 17:30:46 -0400 [thread overview]
Message-ID: <46F04386.8010209@garzik.org> (raw)
In-Reply-To: <alpine.LFD.0.999.0709181408390.16478@woody.linux-foundation.org>
Linus Torvalds wrote:
> The old situation with SATA drivers that had
>
> if (iomem)
> writel(..)
> else
> outl(..)
>
> in the cases that needed it (and used hardcoded writel/outl in the cases
> that didn't) was an example of code that "in theory" is faster. But
> dammit, in practice that mattered not one whit, and what iomap() tries to
> do is to attack the _real_ problem we had in that area.
>
> Which had nothing what-so-ever to do with any branches.
And none of those issues are a factor at all in ath5k (which spawned
this sub-discussion), or indeed many other drivers. The above code you
cite is -generic-, hardware agnostic code.
Most new hardware is MMIO-only, making ioread32() only for drivers that
care about legacy IO support, something that is being slowly phased out.
e.g. legacy IDE, legacy 10/100 mbps ethernet NICs with the dual
MMIO/PIO register spaces.
Jeff
next prev parent reply other threads:[~2007-09-18 21:30 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-17 20:22 [PATCH] Clarify pci_iomap() usage for MMIO-only devices Luis R. Rodriguez
2007-09-18 10:34 ` Alan Cox
2007-09-18 18:46 ` Luis R. Rodriguez
2007-09-18 19:03 ` Linus Torvalds
2007-09-18 19:07 ` Luis R. Rodriguez
2007-09-18 19:22 ` Linus Torvalds
2007-09-18 20:12 ` Luis R. Rodriguez
2007-09-18 20:30 ` Linus Torvalds
2007-09-18 21:02 ` Luis R. Rodriguez
2007-09-18 21:14 ` Linus Torvalds
2007-09-18 21:30 ` Jeff Garzik [this message]
2007-09-18 21:42 ` Linus Torvalds
2007-09-18 22:25 ` Linus Torvalds
2007-09-18 22:21 ` Benjamin Herrenschmidt
2007-09-18 22:36 ` Linus Torvalds
2007-09-18 20:21 ` Jeff Garzik
2007-09-18 22:20 ` Benjamin Herrenschmidt
2007-09-18 23:08 ` Jeff Garzik
2007-09-18 23:27 ` Linus Torvalds
2007-09-18 22:16 ` Benjamin Herrenschmidt
2007-09-18 22:25 ` Alan Cox
2007-09-19 15:07 ` Nick Kossifidis
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