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,
        hal.rosenstock@gmail.com, linux-rdma@vger.kernel.org,
        luto@amacapital.net, mst@redhat.com, linux-kernel@vger.kernel.org,
        cocci@systeme.lip6.fr, "Luis R. Rodriguez" <mcgrof@suse.com>,
        Toshi Kani <toshi.kani@hp.com>,
        Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>,
        Mike Marciniszyn <mike.marciniszyn@intel.com>,
        Roland Dreier <roland@purestorage.com>,
        Dennis Dalessandro <dennis.dalessandro@intel.com>,
        Suresh Siddha <sbsiddha@gmail.com>, Ingo Molnar <mingo@elte.hu>,
        Thomas Gleixner <tglx@linutronix.de>, Juergen Gross <jgross@suse.com>,
        Daniel Vetter <daniel.vetter@ffwll.ch>,
        Dave Airlie <airlied@redhat.com>, Bjorn Helgaas <bhelgaas@google.com>,
        Antonino Daplas <adaplas@gmail.com>,
        Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
        Tomi Valkeinen <tomi.valkeinen@ti.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Arnd Bergmann <arnd@arndb.de>,
        Stefan Bader <stefan.bader@canonical.com>, konrad.wilk@oracle.com,
        ville.syrjala@linux.intel.com, david.vrabel@citrix.com,
        jbeulich@suse.com,
        Roger Pau =?iso-8859-1?Q?Monn=E9?= <roger.pau@citrix.com>,
        linux-fbdev@vger.kernel.org, xen-devel@lists.xensource.com
Subject: Re: [PATCH v4 2/2] IB/qib: use arch_phys_wc_add()
Message-ID: <20150421221718.GA10836@obsidianresearch.com>
References: <1429653035-19424-1-git-send-email-mcgrof@do-not-panic.com>
 <1429653035-19424-3-git-send-email-mcgrof@do-not-panic.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1429653035-19424-3-git-send-email-mcgrof@do-not-panic.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1200
Lines: 36

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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/