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Subject: Re: [PATCH] powerpc: Add MPC837x PCIE controller RC mode support
From: Li Li <r64360@freescale.com>
To: Arnd Bergmann <arnd@arndb.de>
In-Reply-To: <200801030914.12628.arnd@arndb.de>
References: <1199272605.22416.8.camel@Guyver>
	<200801021253.08280.arnd@arndb.de> <1199342440.7375.29.camel@Guyver>
	<200801030914.12628.arnd@arndb.de>
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Date: Thu, 03 Jan 2008 16:31:06 +0800
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Cc: Wood Scott <scottwood@freescale.com>, linuxppc-dev@ozlabs.org,
	Phillips Kim <Kim.Phillips@freescale.com>, Li Tony <Tony.Li@freescale.com>
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On Thu, 2008-01-03 at 16:14 +0800, Arnd Bergmann wrote:
> On Thursday 03 January 2008, Li Li wrote: 
> > > * The detection method for the primary bus is somewhat fragile, 
> > > because 
> > > we depend on the order of the nodes in the device tree, which is
> not 
> > > specified to have a meaning. /Maybe/ there could be a property in 
> > > (at most) one of the PCI host bridge nodes saying that this
> specific 
> > > bus 
> > > is the primary one. 
> > > 
> > 
> > Put this primary in code is more save than in dts. 
> > The dts lacks error checking function. If provide error dts such as
> two 
> > pci hosts both has primary property will occur chaos.
> 
> It's easy enough to just panic() if you find more than one primary
> bus, 
> since the information from the device tree is static enough that one 
> will know how to fix this after seeing the error.
> 

It is just a case. what about if do not find primary pci host.
The current code can prevent this potential error and make system
robust.

- Tony