linux-kernel - Re: [PATCH V12 2/4] ptp: Added a clock that uses the eTSEC found on the MPC85xx.

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Date:	Sat, 26 Mar 2011 14:23:48 +0100
From:	Richard Cochran <richardcochran@...il.com>
To:	John Stultz <john.stultz@...aro.org>
Cc:	linux-kernel@...r.kernel.org, linux-api@...r.kernel.org,
	netdev@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	linux-arm-kernel@...ts.infradead.org,
	linuxppc-dev@...ts.ozlabs.org, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Arnd Bergmann <arnd@...db.de>,
	Christoph Lameter <cl@...ux.com>,
	David Miller <davem@...emloft.net>,
	Krzysztof Halasa <khc@...waw.pl>,
	Peter Zijlstra <peterz@...radead.org>,
	Rodolfo Giometti <giometti@...ux.it>,
	Thomas Gleixner <tglx@...utronix.de>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Mike Frysinger <vapier@...too.org>,
	Paul Mackerras <paulus@...ba.org>,
	Russell King <linux@....linux.org.uk>
Subject: Re: [PATCH V12 2/4] ptp: Added a clock that uses the eTSEC found
 on the MPC85xx.

On Wed, Mar 23, 2011 at 02:30:04PM -0700, John Stultz wrote:
> On Mon, 2011-02-28 at 08:57 +0100, Richard Cochran wrote:
> > +/*
> > + * Register access functions
> > + */
> 
> So what are the locking rules on the functions below? I assume the
> etsects->lock needs to be held prior to calling, so that should be made
> explicit in a comment.

Yes, you are right. I'll add comments.

> > +	gfar_write(&etsects->regs->tmr_ctrl,   tmr_ctrl);
> > +	gfar_write(&etsects->regs->tmr_add,    etsects->tmr_add);
> > +	gfar_write(&etsects->regs->tmr_prsc,   etsects->tmr_prsc);
> > +	gfar_write(&etsects->regs->tmr_fiper1, etsects->tmr_fiper1);
> > +	gfar_write(&etsects->regs->tmr_fiper2, etsects->tmr_fiper2);
> > +	set_alarm(etsects);
> > +	gfar_write(&etsects->regs->tmr_ctrl,   tmr_ctrl|FS|RTPE|TE);
> 
> Does any of the above need a lock should an irq land in the middle of
> the writes?

Since these interrupts first must be enabled, I think it unlikely that
an IRQ could occur. However, it can't hurt to add the lock, either.

Thanks,

Richard
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