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

[Paul Mackerras]

David Edelsohn <dje at watson.ibm.com> wrote:

> 	Is your assumption that you want to provide the infrastructure to
> write high-performance device drivers or to write device drivers that
> don't require as much expertise and knowledge to produce correct results?

Interesting question.

I guess I would be trying both to make it easy to write device drivers
that work, and possible to write very high-performance device drivers.
Particularly since the vast majority of drivers in Linux have been
written for the i386 platform, which doesn't do pesky (;-) things like
reordering reads and writes.

In any case, as far as the question of using readl/writel in
framebuffer code goes, and whether readl/writel should include the
eieio, the measurements I did showed zero performance impact of having
the eieio, in frame-buffer copy code at least.

Paul.

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