Re: [PATCH v3 18/18] infiniband: cxgb4: Eliminate duplicate barriers on weakly-ordered archs

From: David Miller
Date: Sat Mar 17 2018 - 09:27:59 EST


From: Sinan Kaya <okaya@xxxxxxxxxxxxxx>
Date: Sat, 17 Mar 2018 00:25:14 -0400

> I think I finally got what you mean.
>
> Code seems to have
>
> wmb()
> writel()/writeq()
> wmb()
>
> this can be safely replaced with
>
> wmb()
> __raw_writel()/__raw_writeq()
> wmb()
>
> This will work on all arches. Below is the new version. Let me know if this is OK.

Unfortunately, I think this won't work.

At least on sparc, the __raw_*() variants also change the endianness to
native endianness.

PowerPC does this as well, even documented in a comment :-)

/*
* Non ordered and non-swapping "raw" accessors
*/

Only the non-__raw_ variants do the endianness swap to/from
little-endian.