netdev - Re: [PATCH v3 1/1] net: fec: ptp: avoid register access when ipg clock is disabled

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Message-ID: <20140818194151.GA4048@netboy>
Date:	Mon, 18 Aug 2014 21:42:10 +0200
From:	Richard Cochran <richardcochran@...il.com>
To:	"fugang.duan@...escale.com" <fugang.duan@...escale.com>
Cc:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>
Subject: Re: [PATCH v3 1/1] net: fec: ptp: avoid register access when ipg
 clock is disabled

On Mon, Aug 18, 2014 at 06:07:00AM +0000, fugang.duan@...escale.com wrote:
> 1. Set the flag to false firstly.

Yes.

> 2. Don't need to add mutex to protect the flag.(My previous mail ask one mutex to protect the flag)

You *do* need a mutex to protect the state of the physical clock. One
process might turn it off while another process is still reading it.

>    Just pull the flag into the protected field by spin_lock_irqsave() like :
> fec_time_keep()

No, the spin only protects the register access.

Thanks,
Richard
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