Messages in this thread | | | Date | Mon, 02 Jun 2008 14:18:04 -0400 | From | Loic Prylli <> | Subject | Re: howto use ioremap_wc? |
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On 06/02/2008 12:27 PM, Brice Goglin wrote: > Arjan van de Ven wrote: > >> Ok this leads to a question: since write combining is effectively an >> extension (eg relaxation) to uncached, how much do you care if you >> actually get uncached? Eg can you just use the "WC" function even for >> the case where you get an uncached mapping ? >> >> > > WC is strictly required for our "wcfifo" path,
To be more accurate about the above statement, that codepath will still work correctly even if the mapping ends-up being uncached, but that could lead to a 16X slowdown on some machines, since that path was really designed for the WC case.
Anyway that codepath does not really matter as Brice mentioned afterwards :-)
> but this path is actually > not so important nowadays. It is disabled by default and might even be > removed in the future. So, no, myri10ge itself does not really need to > know whether the mapping is actually WC. >
Loic
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