Re: [PATCH V8 03/10] USB/ppc4xx: Add Synopsys DWC OTG CoreInterface Layer

[Alexander Gordeev <lasaine@lvk.cs.msu.su>]

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В Wed, 26 Jan 2011 16:35:05 -0000
"David Laight" <David.Laight@ACULAB.COM> пишет:

>  
> > Also in_le32/out_le32/in_be32/out_be32 are 
> > architecture-specific AFAIK.
> 
> Isn't the whole patch architecture-specific ?

I use this driver on MIPS board right now. :)
This core from Synopsys is used in many SOCs with various architectures.

> > I'd suggest using readl/writel for LE ops and
> > __be32_to_cpu(__raw_readl(addr))/__raw_writel(__cpu_to_be32(b),addr)
> > for BE ops.
> 
> Since the ppc doesn't have a byteswap instruction (and the LE
> memory transfers might even be slow!) you really don't want to
> be doing software byteswap.
> 
> Not to mention the horrific synchronistion instructions
> that in_le32() and out_le32() actually contain.
> 
> I didn't find __raw_readl() when I was looking for asm
> patterns that byteswapped memory transfers.
> 
> I did find st_le32() and ld_le32() in arch/powerpc/include/asm/swab.h
> but that file is actually quite difficult to #include because
> there is another swab.h that gets included instead.

I see. readl/writel are defined in asm-generic/io.h. So IMHO there
should be also le and be versions that can be redefined in
arch-specific code.

-- 
  Alexander

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