netdev - Re: [PATCH v5 1/1] net: fec: ptp: avoid register access when ipg clock is disabled

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Message-Id: <20140822.104625.2141682975890196702.davem@davemloft.net>
Date:	Fri, 22 Aug 2014 10:46:25 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	b38611@...escale.com
Cc:	richardcochran@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH v5 1/1] net: fec: ptp: avoid register access when ipg
 clock is disabled

From: Fugang Duan <b38611@...escale.com>
Date: Thu, 21 Aug 2014 17:09:38 +0800

> The current kernel hang on i.MX6SX with rootfs mount from MMC.
> The root cause is that ptp uses a periodic timer to access enet register
> even if ipg clock is disabled.
> 
> FEC ptp driver start one period timer to read 1588 counter register in the
> ptp init function that is called after FEC driver is probed.
> 
> To save power, after FEC probe finish, FEC driver disable all clocks including
> ipg clock that is needed for register access.
> 
> i.MX5x, i.MX6q/dl/sl FEC register access don't cause system hang when ipg clock
> is disabled, just return zero value. But for i.MX6sx SOC, it cause system hang.
> 
> To avoid the issue, we need to check ptp clock status before ptp timer count access.
> 
> Signed-off-by: Fugang Duan <B38611@...escale.com>

Applied, thanks.
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