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Date: Tue, 21 Apr 2015 16:17:18 -0600
From: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
To: "Luis R. Rodriguez" <mcgrof@do-not-panic.com>
Cc: infinipath@intel.com, roland@kernel.org, sean.hefty@intel.com,
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Subject: Re: [PATCH v4 2/2] IB/qib: use arch_phys_wc_add()
Message-ID: <20150421221718.GA10836@obsidianresearch.com>
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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