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Subject: Re: [PATCH 2/4] x86/amd_nb: add support for newer PCI topologies
From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>, "Woods, Brian" <Brian.Woods@amd.com>,
 Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H.
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Date: Wed, 07 Nov 2018 15:44:10 -0800
In-Reply-To: <9e4da173ba2978e1c16839162dd927c5ea0fdc36.camel@linux.intel.com>
References: <20181102195925.GB160487@google.com>
	 <20181102232948.GC26770@zn.tnic> <20181105214537.GA19420@google.com>
	 <20181105215650.GG26868@zn.tnic> <20181106214256.GA65443@google.com>
	 <20181106220059.GA4139@zn.tnic> <20181106232040.GA85755@google.com>
	 <75748b089ee696d5cbaa5c0ce68bad228699894c.camel@linux.intel.com>
	 <20181107213103.GA41183@google.com>
	 <baf4b2e9c9b7cb2f827fd3bffce4b72f6d9376a8.camel@linux.intel.com>
	 <20181107231411.GB41183@google.com>
	 <9e4da173ba2978e1c16839162dd927c5ea0fdc36.camel@linux.intel.com>
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On Wed, 2018-11-07 at 15:30 -0800, Srinivas Pandruvada wrote:
> [...]
> 
> > Sure, you can't *force* OEMs to supply a given ACPI device, but you
> > can certainly say "if you want this functionality, supply INT3401
> > devices."  That's what you do with PNP0A03 (PCI host bridges), for
> > example.  If an OEM doesn't supply PNP0A03 devices, the system can
> > boot just fine as long as you don't need PCI.
> > 
> > This model of using the PCI IDs forces OS vendors to release
> > updates
> > for every new platform.  I guess you must have considered that and
> > decided whatever benefit you're getting was worth the cost.
> 
> Not worth cost. This is a pain. Every release we end up adding a
> single
> line change to many drivers adding a PCI device id. 
> Since there is no unique class_mask for PCI device for these devices,
> we need to add device_id for each generation even if there is no
> change.
> Instead if we have some feature to say don't enumerate for PCI device
> id < X and a black list, it will save lot of work.
This still needs some work on our internal PCI device allocation scheme
, where we can reserve a block of ids for a PCI device for same
functionality from generation to generation.

Thanks,
Srinivas