linux-kernel - RE: [PATCH] pci: support Thunderbolt requirements for I/O resources.

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Message-ID: <BC567D27D6B7384F84318942321624DE16179EE6@hasmsx109.ger.corp.intel.com>
Date:	Tue, 18 Nov 2014 08:15:21 +0000
From:	"Jamet, Michael" <michael.jamet@...el.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Levy, Amir (Jer)" <amir.jer.levy@...el.com>,
	"Alloun, Dan" <dan.alloun@...el.com>,
	Rafael Wysocki <rjw@...ysocki.net>,
	Andreas Noever <andreas.noever@...il.com>
Subject: RE: [PATCH] pci: support Thunderbolt requirements for I/O resources.

> -----Original Message-----
> From: Andy Shevchenko [mailto:andy.shevchenko@...il.com]
> Sent: Wednesday, November 12, 2014 20:31
> To: Bjorn Helgaas
> Cc: Jamet, Michael; linux-pci@...r.kernel.org; linux-kernel@...r.kernel.org;
> Levy, Amir (Jer); Alloun, Dan; Rafael Wysocki; Andreas Noever
> Subject: Re: [PATCH] pci: support Thunderbolt requirements for I/O
> resources.
> 
> On Wed, Nov 12, 2014 at 7:29 PM, Bjorn Helgaas <bhelgaas@...gle.com>
> wrote:
> 
> []
> 
> >> To prevent this, we detect a chain contains a Thunderbolt device by
> >> checking the Thunderbolt PCI device id.
> >
> > I'm really not happy about checking a list of device IDs to identify
> > Thunderbolt devices.  Surely there's a better way, because a list like
> > this has to be updated regularly.
> 
> I recently proposed internally to use quirks (pci_fixup_early) for that, but
> apparently Michael didn't have time to answer. It might be he can just
> comment here since the patch already public.
> 
> --
> With Best Regards,
> Andy Shevchenko

Indeed, I've explored the quirks option.
Unfortunately the fixup hook seems to be called too late in the code 
since pci_enable_device()calls pcibios_enable_device() which actually 
send a PCI command with  CMD |=PCI_COMMAND_IO and configure the PCI HW. 
The IORESOURCE_MEM and IORESOURCE_IO flags are set at the time the
pci_enable_device(), pci_enable_device_mem() or pci_enable_device_io() 
is called during device initializations, so an early fixup call won't help either.
At this stage, the PCI HW is configured and a fixup call won't  resolve the issue
unless another PCI command is sent to revert it 
(generally not advised to execute again on hardware).

Michael 
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