[U-Boot] [PATCH v3 02/10] armv7: add miscellaneous utility macros

Wolfgang Denk
2011-06-08T21:41:24Z

Dear Aneesh V,

In message <4DEF62A6.7060706@ti.com> you wrote:
>
> I still don't think this is the 'right' solution for my problem. I don't
> like the fact that clrsetbits_le32() introduces a lot of un-necessary
> 'volatile's.

Well, with this argument you would also have to refuse using readl()
and writel() and all other I/O accessor macros. The only place where
volatile is used is in the __arch_get*() and __arch_put*() macros, and
ther eit is supposed to be ok.

> Yes, it's about the 'efficiency'. May be it doesn't count in some
> cases. But, may be it counts in some other cases. Basically, I don't
> like to sacrifice 'efficiency' unless the cost for achieving it is very

Try and show me a single case where you see a measurable difference in
performance.

> If you still insist, I can use clrsetbits_le32() in the interest
> of getting this to a closure.

Please do. Thanks.

> We have a set of powerful macros designed for bit-field accesses in IO
> egisters.
>
> But, what I am looking for is a set of macros for bit-field operations
> on C integer variables without the un-necessary overhead of IO register
> accesses. I am looking for missing APIs in bitops.h not anything from
> io.h

All the overhead we have is a few memory barriers. Can you measure
any difference in performance?

Best regards,

Wolfgang Denk

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