PCI: Recognize Thunderbolt devices

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

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 8dd38e69d6f2a8ae4f4b7d6801f3f321abb5ac1a..4dbf9f96ae5ba31d761b30ee43c11d2f053140fe 100644 (file)
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -3,6 +3,8 @@
 
 #define PCI_FIND_CAP_TTL       48
 
+#define PCI_VSEC_ID_INTEL_TBT  0x1234  /* Thunderbolt */
+
 extern const unsigned char pcie_link_speed[];
 
 bool pcie_cap_has_lnkctl(const struct pci_dev *dev);

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index dfc9a27941418976c0fadee7e6628531fbb47613..90592d424e9b67458ad740ddb3b09d50f5ec30ff 100644 (file)
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1208,6 +1208,24 @@ void set_pcie_hotplug_bridge(struct pci_dev *pdev)
                pdev->is_hotplug_bridge = 1;
 }
 
+static void set_pcie_thunderbolt(struct pci_dev *dev)
+{
+       int vsec = 0;
+       u32 header;
+
+       while ((vsec = pci_find_next_ext_capability(dev, vsec,
+                                                   PCI_EXT_CAP_ID_VNDR))) {
+               pci_read_config_dword(dev, vsec + PCI_VNDR_HEADER, &header);
+
+               /* Is the device part of a Thunderbolt controller? */
+               if (dev->vendor == PCI_VENDOR_ID_INTEL &&
+                   PCI_VNDR_HEADER_ID(header) == PCI_VSEC_ID_INTEL_TBT) {
+                       dev->is_thunderbolt = 1;
+                       return;
+               }
+       }
+}
+
 /**
  * pci_ext_cfg_is_aliased - is ext config space just an alias of std config?
  * @dev: PCI device
@@ -1360,6 +1378,9 @@ int pci_setup_device(struct pci_dev *dev)
        /* need to have dev->class ready */
        dev->cfg_size = pci_cfg_space_size(dev);
 
+       /* need to have dev->cfg_size ready */
+       set_pcie_thunderbolt(dev);
+
        /* "Unknown power state" */
        dev->current_state = PCI_UNKNOWN;
 

diff --git a/include/linux/pci.h b/include/linux/pci.h
index eb3da1a04e6cdc7d3f4efab5532f53abcdf3a28f..5948cfdc984e2f849507fa1d0fb8f2bed3c01cfa 100644 (file)
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -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>