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. Add a helper to check
whether a given PCI device is situated on a Thunderbolt daisy chain.
The necessity arises from the following:
* To power off Thunderbolt controllers on Macs even if their BIOS is
older than 2015, their PCIe ports need to be whitelisted for runtime
PM. 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 on a Thunderbolt daisy
chain.
Cc: Andreas Noever <andreas.noever@xxxxxxxxx>
Cc: Michael Jamet <michael.jamet@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 | 21 +++++++++++++++++++++
include/linux/pci.h | 23 +++++++++++++++++++++++
3 files changed, 46 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..7963ecc6d85f 100644
--- 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 e2d1a124216a..36dfcfd946f4 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; /* Thunderbolt controller */
unsigned int __aer_firmware_first_valid:1;
unsigned int __aer_firmware_first:1;
unsigned int broken_intx_masking:1;
@@ -2171,6 +2172,28 @@ 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 soldered to the mainboard.
+ */
+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>
--
2.11.0
