[ofa-general] Write combining support in OFED 1.5

[Jack Morgenstein]

On Tuesday 07 July 2009 13:03, Or Gerlitz wrote:
> Jack Morgenstein wrote:
> > I've been looking at the write-combining support in the 2.6.30 kernel, and it looks good [...] from the write-combining support in OFED 1.4:
> >   
> Hi Jack, is there some WC related code which is in ofed but not in 
> mainline? why?
> 
> Or.

Yes, there is (see kernel_patches/fixes/mlx4_0010_add_wc.patch).

OFED 1.4 is based on kernel 2.6.27, which did not have kernel-based WC support --
this support was put in the kernel only in kernel 2.6.29.

With OFED 1.5, I am trying to use the kernel-based WC support, and eliminate the patch.
To do this, I need 2 things:

1. macro pgprot_writecombine to be defined for PPC/PPC64 under the arch directory
   (file arch/powerpc/include/asm/pgtable.h)
2. A way of determining (via the standard kernel) if write-combining is available
   on a given platform (to allow disabling use of ConnectX blueflame in userspace if WC is not available).

-Jack