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PCI: Recognize Thunderbolt devices

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Detect on probe whether a PCI device is part of a Thunderbolt controller.
Intel uses a Vendor-Specific Extended Capability (VSEC) with ID 0x1234
on such devices.  Detect presence of this VSEC and cache it in a newly
added is_thunderbolt bit in struct pci_dev.

Also, add a helper to check whether a given PCI device is situated on a
Thunderbolt daisy chain (i.e., below a PCI device with is_thunderbolt
set).

The necessity arises from the following:

* If an external Thunderbolt GPU is connected to a dual GPU laptop,
  that GPU is currently registered with vga_switcheroo even though it
  can neither drive the laptop's panel nor be powered off by the
  platform.  To vga_switcheroo it will appear as if two discrete
  GPUs are present.  As a result, when the external GPU is runtime
  suspended, vga_switcheroo will cut power to the internal discrete GPU
  which may not be runtime suspended at all at this moment.  The
  solution is to not register external GPUs with vga_switcheroo, which
  necessitates a way to recognize if they're on a Thunderbolt daisy
  chain.

* Dual GPU MacBook Pros introduced 2011+ can no longer switch external
  DisplayPort ports between GPUs.  (They're no longer just used for DP
  but have become combined DP/Thunderbolt ports.)  The driver to switch
  the ports, drivers/platform/x86/apple-gmux.c, needs to detect presence
  of a Thunderbolt controller and, if found, keep external ports
  permanently switched to the discrete GPU.

v2: Make kerneldoc for pci_is_thunderbolt_attached() more precise,
    drop portion of commit message pertaining to separate series.
    (Bjorn Helgaas)

Cc: Andreas Noever <andreas.noever@gmail.com>
Cc: Michael Jamet <michael.jamet@intel.com>
Cc: Tomas Winkler <tomas.winkler@intel.com>
Cc: Amir Levy <amir.jer.levy@intel.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: http://patchwork.freedesktop.org/patch/msgid/0ab165a4a35c0b60f29d4c306c653ead14fcd8f9.1489145162.git.lukas@wunner.de
This commit is contained in:
Lukas Wunner
2017-03-10 21:23:45 +01:00
parent 8ccd1e5162
commit 8531e283be
3 changed files with 46 additions and 0 deletions
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23
include/linux/pci.h
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@@ -358,6 +358,7 @@ struct pci_dev {
unsigned int is_virtfn:1;
unsigned int reset_fn:1;
unsigned int is_hotplug_bridge:1;
unsigned int is_thunderbolt:1; /* Thunderbolt controller */
unsigned int __aer_firmware_first_valid:1;
unsigned int __aer_firmware_first:1;
unsigned int broken_intx_masking:1;
@@ -2160,6 +2161,28 @@ static inline bool pci_ari_enabled(struct pci_bus *bus)
return bus->self && bus->self->ari_enabled;
}
/**
* pci_is_thunderbolt_attached - whether device is on a Thunderbolt daisy chain
* @pdev: PCI device to check
*
* Walk upwards from @pdev and check for each encountered bridge if it's part
* of a Thunderbolt controller. Reaching the host bridge means @pdev is not
* Thunderbolt-attached. (But rather soldered to the mainboard usually.)
*/
static inline bool pci_is_thunderbolt_attached(struct pci_dev *pdev)
{
struct pci_dev *parent = pdev;
if (pdev->is_thunderbolt)
return true;
while ((parent = pci_upstream_bridge(parent)))
if (parent->is_thunderbolt)
return true;
return false;
}
/* provide the legacy pci_dma_* API */
#include <linux/pci-dma-compat.h>