netdev - Re: FEC driver hangs hardware on i.MX6SX

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Date:	Mon, 21 Jul 2014 09:59:16 +0800
From:	Shawn Guo <shawn.guo@...escale.com>
To:	Richard Cochran <richardcochran@...il.com>
CC:	Fugang Duan <B38611@...escale.com>,
	<linux-arm-kernel@...ts.infradead.org>, <netdev@...r.kernel.org>,
	Frank Li <Frank.li@...escale.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: FEC driver hangs hardware on i.MX6SX

On Sun, Jul 20, 2014 at 08:20:49AM +0200, Richard Cochran wrote:
> On Sun, Jul 20, 2014 at 10:57:33AM +0800, Shawn Guo wrote:
> > 
> > I think the cause is that PTP is still accessing registers after FEC
> > driver calls fec_enet_clk_enable(ndev, false) to disable FEC clocks.
> > Can you please try to provide a fix for this regression soon?
> 
> What do you mean by, "PTP is still accessing registers"?
> 
> The only access to any register is through the driver, and the driver
> can and should make sure all register accesses are safe.

Sorry for being vague, Richard.  I meant PTP driver is still accessing
registers.

With Fugang's clock management patch, FEC clocks will be disabled to
save power after FEC gets probed.  But at that point, fec_ptp driver
already launches a timer, which will trigger the read on FEC ATIME
register once per second.

Shawn
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