[linux-fbdev] Re: readl() and friends and eieio on PPC

[Jes Sorensen]

>>>>> "David" == David Edelsohn <dje at watson.ibm.com> writes:

>>>>> Richard Henderson writes:
Richard> But it isn't zero cost.  It's not high cost, but that's not
Richard> the same thing.

David> 	Is your assumption that you want to provide the infrastructure
David> to write high-performance device drivers or to write device
David> drivers that don't require as much expertise and knowledge to
David> produce correct results?  There are conflicting goals in this
David> design providing different benefits to Linux.

I am certainly up for high performance device drivers. Even having
writel do the syncing there are enough other pitfalls for people to
take into account. Some of these are much harder to understand than
dealing with write ordering and as such, trying to make things
invisible are only giving us a false guarantee. Ie. if we want to use
spin locks in the kernel we need to teach people how to use them
correctly.

Jes

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