Re: [PATCH v4 2/2] IB/qib: use arch_phys_wc_add()

Jason Gunthorpe
2015-04-21T22:17:18Z

On Tue, Apr 21, 2015 at 02:50:35PM -0700, Luis R. Rodriguez wrote:
> - if (qib_wc_pat) {
> - resource_size_t vl15off;
> - /*
> - * We do not set WC on the VL15 buffers to avoid
> - * a rare problem with unaligned writes from
> - * interrupt-flushed store buffers, so we need
> - * to map those separately here. We can't solve
> - * this for the rarely used mtrr case.
> - */
> - ret = init_chip_wc_pat(dd, 0);
> - if (ret)
> - goto bail;
> + /*
> + * We do not set WC on the VL15 buffers to avoid
> + * a rare problem with unaligned writes from
> + * interrupt-flushed store buffers, so we need
> + * to map those separately here. We can't solve
> + * this for the rarely used mtrr case.
> + */

This is a small change in behavior, but it doesn't seem important..

Mike, what do you think about adding:

if (dd->wc_cookie)
dev_err(.., "Using this device without CPU PAT support is known to be broken");

or similar..

Jason