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Kernel v4.15 added support for native enumeration of Thunderbolt topology. The enumeration mode affects both the BIOS and TBT FW operation so they must agree on it. Platforms may support both modes, native and "legacy" (or "BIOS-assist"). This change makes sure the new image is compatible with the current controller mode (otherwise the BIOS and TBT FW will not be alligned on it at least until next boot) and also adds a new GUID generation logic for a controller in "native" mode so LVFS could contain 2 images, one for the "legacy" mode and one for "native". Signed-off-by: Yehezkel Bernat <yehezkel.bernat@intel.com>
55 lines
2.3 KiB
Markdown
55 lines
2.3 KiB
Markdown
Thunderbolt™ Support
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====================
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Introduction
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------------
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Thunderbolt™ is the brand name of a hardware interface developed by Intel that
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allows the connection of external peripherals to a computer.
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Versions 1 and 2 use the same connector as Mini DisplayPort (MDP), whereas
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version 3 uses USB Type-C.
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Runtime Power Management
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------------------------
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Thunderbolt controllers are slightly unusual in that they power down completely
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when no thunderbolt devices are detected. This poses a problem for fwupd as
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it can't coldplug devices to see if there are firmware updates available, and
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also can't ensure the controller stays awake during a firmware upgrade.
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On Dell hardware the `Thunderbolt::CanForcePower` metadata value is set as the
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system can force the thunderbolt controller on during coldplug or during the
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firmware update process. This is typically done calling a SMI or ACPI method
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which asserts the GPIO for the duration of the request.
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On non-Dell hardware you will have to insert a Thunderbolt device (e.g. a dock)
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into the laptop to be able to update the controller itself.
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Safe Mode
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---------
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Thunderbolt hardware is also slightly unusual in that it goes into "safe mode"
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whenever it encounters a critical firmware error, for instance if an update
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failed to be completed. In this safe mode you cannot query the controller vendor
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or model and therefore the thunderbolt plugin cannot add the correct GUID used
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to match it to the correct firmware.
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In this case the metadata value `Thunderbolt::IsSafeMode` is set which would
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allow a different plugin to add the correct GUID based on some out-of-band
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device discovery. At the moment this only happens on Dell hardware.
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GUID generation for LVFS
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------------------------
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The GUID for the controller, which must appear in the metadata when uploading an
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NVM to LVFS, can be generated by a tool like `appstream-util` (with
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`generate-guid` command) or by Python (with
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`uuid.uuid5(uuid.NAMESPACE_DNS, 'string')`).
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The format of the string used as input is "TBT-vvvvdddd", where vvvvv is the
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vendor ID and dddd is the device ID, both in hex, as appear in the controller's
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DROM and exposed in the relevant sysfs attributes.
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If the controller is in native enumeration mode, the string "-native" is added
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at the end so the format is "TBT-vvvvdddd-native".
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