linux-kernel - Re: [PATCH v7 1/5] powerpc/85xx: implement hardware timebase sync

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Message-ID: <20120704031426.GA6133@localhost.localdomain>
Date:	Wed, 4 Jul 2012 11:14:26 +0800
From:	Zhao Chenhui <chenhui.zhao@...escale.com>
To:	Tabi Timur-B04825 <B04825@...escale.com>
CC:	Zhao Chenhui-B35336 <B35336@...escale.com>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Wood Scott-B07421 <B07421@...escale.com>,
	"galak@...nel.crashing.org" <galak@...nel.crashing.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	<leoli@...escale.com>
Subject: Re: [PATCH v7 1/5] powerpc/85xx: implement hardware timebase sync

On Tue, Jul 03, 2012 at 07:46:24AM -0500, Tabi Timur-B04825 wrote:
> On Tue, Jul 3, 2012 at 5:21 AM, Zhao Chenhui <chenhui.zhao@...escale.com> wrote:
> 
> > +       np = of_find_matching_node(NULL, mpc85xx_smp_guts_ids);
> > +       if (np) {
> > +               guts = of_iomap(np, 0);
> > +               of_node_put(np);
> > +               if (!guts) {
> > +                       pr_err("%s: Could not map guts node address\n",
> > +                                                               __func__);
> > +                       return;
> > +               }
> > +               smp_85xx_ops.give_timebase = mpc85xx_give_timebase;
> > +               smp_85xx_ops.take_timebase = mpc85xx_take_timebase;
> > +       }
> 
> I had this in mind:
> 
>                guts = of_iomap(np, 0);
>                of_node_put(np);
>                if (guts) {
>                        smp_85xx_ops.give_timebase = mpc85xx_give_timebase;
>                        smp_85xx_ops.take_timebase = mpc85xx_take_timebase;
>                 } else {
>                        pr_err("%s: Could not map guts node address\n",
>                                                                __func__);
>                }
> 
> That way, a missing GUTS node does not break everything.
> 

If the guts variable is NULL, it indicates there is error in dts or kernel.
We should fix the error, rather than ignore it.

Moreover, if smp_85xx_ops.give/take_timebase is NULL, kernel can not do the timebase sync.

-Chenhui

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