linux-kernel - Re: [PATCH 4.2 108/110] pinctrl: baytrail: Serialize all register access

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Date:	Sun, 08 Nov 2015 09:38:29 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Cc:	stable@...r.kernel.org, Linus Walleij <linus.walleij@...aro.org>,
	Lucas De Marchi <lucas.de.marchi@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4.2 108/110] pinctrl: baytrail: Serialize all register
 access

On Fri, 2015-11-06 at 11:19 -0800, Greg Kroah-Hartman wrote:
> 4.2-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Mika Westerberg <mika.westerberg@...ux.intel.com>
> 
> commit 39ce8150a079e3ae6ed9abf26d7918a558ef7c19 upstream.
> 
> There is a hardware issue in Intel Baytrail where concurrent GPIO register
> access might result reads of 0xffffffff and writes might get dropped
> completely.
> 
> Prevent this from happening by taking the serializing lock in all places
> where it is possible that more than one thread might be accessing the
> hardware concurrently.
[...]

While I have no objection to this, I think a complete fix requires
adding mmiowb() before each spin_unlock.

Ben.

-- 
Ben Hutchings
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