Re: ioremap_uc() followed by set_memory_wc() - burrying MTRR

Jason Gunthorpe
2015-04-21T22:57:32Z

On Wed, Apr 22, 2015 at 12:46:01AM +0200, Luis R. Rodriguez wrote:

> are talking about annotating the qib driver as "known to be broken without PAT"
> and since the ipath driver needs considerable work to be ported to
> use PAT (the

This only seems to be true for one of the chips that driver supports,
not all possibilities.

> userspace register is just one area) I wanted to review if we can just remove
> MTRR use on the ipath driver and annotate write-combining with PAT as a TODO
> item.

AFAIK, dropping MTRR support will completely break the performance to
the point the driver is unusable. If we drop MTRR we may as well
remove the driver.

Mike, do you think the time is right to just remove the iPath driver?

Jason