Messages in this thread |  | | | Subject | Re: lib/iomap.c mmio_{in,out}s* vs. __raw_* accessors | | From | Benjamin Herrenschmidt <> | | Date | Sun, 05 Nov 2006 15:38:57 +1100 |
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> The _only_ reason to use "ioread32be()" would be because the machine is > actually natively BE, and you want to avoid swab. That's kind of the point > of using "be32_to_cpu(__raw_readl(addr)))" like we do now - it will do the > byte swap only if it's necessary. > > In contrast, your "swab(readl())" does _two_ byteswaps - once to turn it > into LE, then to turn it back into BE.
I'm not doing a swab(readl()), I'm doing a swab(insl()) and have the arch provide a native BE accessor for readl_be(). The idea is that I don't want to add _be accessors for PIO and PIO is slow anyway. But I'm providing one for MMIO, along with the repeat versions. Have a second look.
> So if we can't just rip it out, then we sure as hell shouldn't replace it > with something that is obviously worse either. > > In other words - I don't see the reasoning here again. You seem to want to > make the code just worse.
Wait, let's make thing clear, there are 2 things here:
- MMIO : For that, I'm providing readw_be etc... which my patch defines based on __raw_* just as your suggest, I'm just adding a way for the arch to provide its own.
- PIO : This is broken -now-. The current code doesn't swap at all in the PIO case, thus you get LE result when using ioread32be() on PIO. I propose to fix that with swab() because PIO sucks already, there is no "__raw" for PIO and it doesn't deserve new accessors nor speed.
Cheers, Ben.
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