Detect on device probe whether a PCI device is part of a Thunderbolt
daisy chain (i.e. it is either part of a Thunderbolt controller or part
of the hierarchy below a Thunderbolt controller).
Intel uses a Vendor-Specific Extended Capability (VSEC) with ID 0x1234
on devices belonging to a Thunderbolt controller. Detect presence of
this VSEC on the device itself or on one of its parents and cache it in
a newly added is_thunderbolt bit in struct pci_dev.
The necessity arises from the following:
* To power off Thunderbolt controllers on Macs when nothing is plugged
in, we need to allow runtime PM on their PCIe ports in
pci_bridge_d3_possible(). For this we need a way to recognize them.
* 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.
* If an external Thunderbolt GPU is connected to a dual GPU laptop (Mac
or not), 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 part of a Thunderbolt daisy
chain.
Cc: Andreas Noever <andreas.noever@xxxxxxxxx>
Cc: Tomas Winkler <tomas.winkler@xxxxxxxxx>
Cc: Amir Levy <amir.jer.levy@xxxxxxxxx>
Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
---
drivers/pci/pci.h | 2 ++
drivers/pci/probe.c | 32 ++++++++++++++++++++++++++++++++
include/linux/pci.h | 1 +
3 files changed, 35 insertions(+)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index cb17db242f30..45c2b8144911 100644
--- 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 204960e70333..2fcbc535786e 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1208,6 +1208,35 @@ void set_pcie_hotplug_bridge(struct pci_dev *pdev)
pdev->is_hotplug_bridge = 1;
}
+static void set_pcie_thunderbolt(struct pci_dev *dev)
+{
+ struct pci_dev *parent = dev;
+ int vsec = 0;
+ u32 header;
+
+ /* Is the device part of a Thunderbolt controller? */
+ while ((vsec = pci_find_next_ext_capability(dev, vsec,
+ PCI_EXT_CAP_ID_VNDR))) {
+ pci_read_config_dword(dev, vsec + PCI_VNDR_HEADER, &header);
+ if (dev->vendor == PCI_VENDOR_ID_INTEL &&
+ PCI_VNDR_HEADER_ID(header) == PCI_VSEC_ID_INTEL_TBT) {
+ dev->is_thunderbolt = 1;
+ return;
+ }
+ }
+
+ /*
+ * Is the device attached with Thunderbolt? Walk upwards and check for
+ * each encountered bridge if it's part of a Thunderbolt controller.
+ * Reaching the host bridge means dev is soldered to the mainboard.
+ */
+ while ((parent = pci_upstream_bridge(parent)))
+ if (parent->is_thunderbolt) {
+ 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 +1389,9 @@ 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 e2d1a124216a..3c775e8498f1 100644
--- 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; /* part of Thunderbolt daisy chain */
unsigned int __aer_firmware_first_valid:1;
unsigned int __aer_firmware_first:1;
unsigned int broken_intx_masking:1;
--
2.11.0
