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From: Greg KH <greg@kroah.com>
To: Jia Hongtao-B38951 <B38951@freescale.com>
Cc: Rob Herring <robherring2@gmail.com>,
	"devicetree-discuss@lists.ozlabs.org"
	<devicetree-discuss@lists.ozlabs.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Li Yang-R58472 <r58472@freescale.com>
Subject: Re: [PATCH V3 5/6] Avoid duplicate probe for of platform devices
Date: Fri, 6 Jul 2012 09:17:18 -0700	[thread overview]
Message-ID: <20120706161718.GA26894@kroah.com> (raw)
In-Reply-To: <412C8208B4A0464FA894C5F0C278CD5D01A168F2@039-SN1MPN1-002.039d.mgd.msft.net>

On Fri, Jul 06, 2012 at 06:07:43AM +0000, Jia Hongtao-B38951 wrote:
> 
> > -----Original Message-----
> > From: Greg KH [mailto:greg@kroah.com]
> > Sent: Friday, July 06, 2012 12:26 PM
> > To: Jia Hongtao-B38951
> > Cc: Rob Herring; devicetree-discuss@lists.ozlabs.org; linux-
> > kernel@vger.kernel.org; Li Yang-R58472
> > Subject: Re: [PATCH V3 5/6] Avoid duplicate probe for of platform devices
> > 
> > On Fri, Jul 06, 2012 at 02:05:05AM +0000, Jia Hongtao-B38951 wrote:
> > > Hi Rob and Greg KH,
> > >
> > > Do you have any better idea to avoid duplication probe warning?
> > 
> > I have no idea what the problem is that you are trying to solve.
> > 
> > > > On 06/08/2012 04:43 AM, Jia Hongtao wrote:
> > > > > We changed the pcie controller driver to platform driver so that
> > the
> > > > PCI
> > > > > of platform devices need to be created earlier in the arch_initcall
> > > > stage
> > > > > according to the original timing of calling fsl_add_bridge(). So we
> > do
> > > > PCI
> > > > > probing separately from other devices. But probing more than once
> > could
> > > > > cause duplication warning. We add check if the devices have already
> > > > probed
> > > > > before probing any devices to avoid duplication warning.
> > 
> > Ick, something else is going wrong here, how could you ever have the
> > same device probed more than once?
> > 
> > > > > Signed-off-by: Jia Hongtao <B38951@freescale.com>
> > > > > Signed-off-by: Li Yang <leoli@freescale.com>
> > > > > ---
> > > >
> > > > Where's v1 and v2 history?
> > > >
> > > > >  drivers/of/platform.c |   18 ++++++++++++------
> > > > >  1 files changed, 12 insertions(+), 6 deletions(-)
> > > > >
> > > > > diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> > > > > index a37330e..3aab01f 100644
> > > > > --- a/drivers/of/platform.c
> > > > > +++ b/drivers/of/platform.c
> > > > > @@ -139,6 +139,18 @@ struct platform_device *of_device_alloc(struct
> > > > device_node *np,
> > > > >  	if (!dev)
> > > > >  		return NULL;
> > > > >
> > > > > +	dev->dev.of_node = of_node_get(np);
> > > > > +	if (bus_id)
> > > > > +		dev_set_name(&dev->dev, "%s", bus_id);
> > > > > +	else
> > > > > +		of_device_make_bus_id(&dev->dev);
> > > > > +
> > > > > +	if (kset_find_obj(dev->dev.kobj.kset, kobject_name(&dev-
> > >dev.kobj)))
> > 
> > Whatever you are trying to do here, odds are, it's wrong :)
> > 
> > What is happening that is causing the problem?  What is causing the
> > platform core to be calling probe on a device more than once?
> > 
> > greg k-h
> 
> This is why in some cases we may probe twice:
> Firstly, we need to probe pci controller separately. But in KVM different
> topology of device tree is used in which pci nodes are not under root node
> but under "simple bus". Unfortunately, of_platform_bus_probe() will probe
> all the first level nodes under "simple bus" so pci nodes will probe again.

Sounds like a bug :)

> Two ways to solve this problem:
> 1. All the nodes that need to be probed should just under root.

That seems reasonable.

> 2. Avoid duplication probe at runtime like this patch did.

No, don't paper over the real problem in the platform core code like
this.  Fix the real issue here instead.

> I do like the first one but it's hard to changing the traditional way that
> exist for a long time.

I don't understand, why is this just showing up now?  What changed to
cause this?  Couldn't that be the real problem here?

greg k-h

  reply	other threads:[~2012-07-06 16:17 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-08  9:43 [PATCH V3 5/6] Avoid duplicate probe for of platform devices Jia Hongtao
2012-06-11 15:33 ` Rob Herring
2012-06-12  2:16   ` Jia Hongtao-B38951
     [not found]   ` <4FD60FB1.7050106-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2012-07-06  2:05     ` Jia Hongtao-B38951
2012-07-06  4:26       ` Greg KH
     [not found]         ` <20120706042611.GA1841-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2012-07-06  6:07           ` Jia Hongtao-B38951
2012-07-06 16:17             ` Greg KH [this message]
     [not found]               ` <20120706161718.GA26894-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2012-07-09  2:34                 ` Jia Hongtao-B38951
     [not found]                   ` <412C8208B4A0464FA894C5F0C278CD5D01A1E694-TcFNo7jSaXPiTqIcKZ1S2K4g8xLGJsHaLnY5E4hWTkheoWH0uzbU5w@public.gmane.org>
2012-07-09  3:46                     ` Li Yang-R58472
2012-07-09 13:58                       ` Rob Herring
2012-07-10  2:29                         ` Jia Hongtao-B38951
2012-07-09 14:58                       ` Greg KH
     [not found]                         ` <20120709145831.GB3961-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2012-07-11 18:01                           ` Grant Likely

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