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From: Brice Goglin <brice@myri.com>
To: LKML <linux-kernel@vger.kernel.org>,
	netdev@vger.kernel.org,
	"venkatesh.pallipadi@intel.com" <venkatesh.pallipadi@intel.com>
Subject: howto use ioremap_wc?
Date: Sat, 31 May 2008 11:02:54 +0200	[thread overview]
Message-ID: <4841143E.5080003@myri.com> (raw)

Hello,

We're looking at using ioremap_wc() in myri10ge. No drivers seem to be
using it yet, so I'd like to get some clarification regarding ioremap_wc
failures, MTRR and so on.

What we currently do is mtrr_add() and then ioremap. Depending on the
mtrr_add() success, we use the "wc_fifo" or regular PIO with fences to
submit requests to the NIC. How are we supposed to switch this to
ioremap_wc?

Are we sure that if the arch supports _wc, it does not return success
when the underlying plain ioremap worked but setting up _wc() failed? If
so, why does it revert to ioremap_nocache when PAT isn't enabled?

Can we keep the mtrr_add() in the regular path? Or are we supposed to
drop it when the arch provides ioremap_wc and it did not fail?

thanks,
Brice


             reply	other threads:[~2008-05-31  9:03 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-05-31  9:02 Brice Goglin [this message]
2008-06-01  1:54 ` howto use ioremap_wc? Arjan van de Ven
2008-06-02 16:27   ` Brice Goglin
2008-06-02 18:18     ` Loic Prylli
2008-06-03  2:18     ` Arjan van de Ven
2008-06-05  4:53   ` Roland Dreier

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