Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754780AbaKRP6u (ORCPT ); Tue, 18 Nov 2014 10:58:50 -0500 Received: from mail-qg0-f49.google.com ([209.85.192.49]:59724 "EHLO mail-qg0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754203AbaKRP6s (ORCPT ); Tue, 18 Nov 2014 10:58:48 -0500 MIME-Version: 1.0 In-Reply-To: References: <1415847123-15558-1-git-send-email-michael.jamet@intel.com> From: Bjorn Helgaas Date: Tue, 18 Nov 2014 08:58:28 -0700 Message-ID: Subject: Re: [PATCH] pci: support Thunderbolt requirements for I/O resources. To: "Jamet, Michael" Cc: "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Levy, Amir (Jer)" , "Alloun, Dan" , Rafael Wysocki , Andreas Noever Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 18, 2014 at 12:57 AM, Jamet, Michael wrote: >> -----Original Message----- >> From: Bjorn Helgaas [mailto:bhelgaas@google.com] >> Sent: Wednesday, November 12, 2014 19:29 >> To: Jamet, Michael >> Cc: linux-pci@vger.kernel.org; linux-kernel@vger.kernel.org; Levy, Amir >> (Jer); Alloun, Dan; Rafael Wysocki; Andreas Noever >> Subject: Re: [PATCH] pci: support Thunderbolt requirements for I/O >> resources. >> >> [+cc Rafael, Andreas] >> >> On Wed, Nov 12, 2014 at 7:52 PM, Michael Jamet >> wrote: >> > Every Thunderbolt-based devices or Thunderbolt-connected devices >> > should not allocate PCI I/O resources per Thunderbolt specs. >> >> Please include a pointer to those specs in the changelog. >> > > Unfortunately these specs are not publically available. > >> > On a Thunderbolt PC, BIOS is responsible to allocate IO resources. >> > Kernel shouldn't allocate the PCI I/O resources as it interferes with >> > BIOS operation. >> > Doing this may cause the devices in the Thunderbolt chain not being >> > detected or added, or worse to stuck the Thunderbolt Host controller. >> >> These new kernel/firmware coordination requirements need to be >> documented. If they're already part of a PCIe ECN or PCI firmware spec, just >> provide a pointer. >> > > Same, this refers to same specs. > >> > 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. >> >> Bjorn >> > > This was also discussed internally and the only way to identify Thunderbolt devices is to check the device IDs. > As you said, this will require us to maintain and keep the list up-to-date as we deliver new devices. I don't really see how this can work. You're asking me to put changes based on a secret spec into generic code that is used on every machine with PCI. I have no way to maintain something like that. This seems like a major screw up in the design and documentation of Thunderbolt. Bjorn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/