[PATCH 2/2] Documentation: explain how to override Thunderbolt Vendor ID

Francisco Blas Izquierdo Riera (klondike)
2021-11-24T16:37:30Z

Update the Thunderbolt documentation to explain how to use the
``switch_nvm_vendor_override`` parameter to be able to reflash
a Thunderbolt controller's NVM reporting an invalid Vendor ID.

Signed-off-by: Francisco Blas Izquierdo Riera (klondike) <klondike@klondike.es>
---
Documentation/admin-guide/thunderbolt.rst | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/Documentation/admin-guide/thunderbolt.rst b/Documentation/admin-guide/thunderbolt.rst
index 2ed79f41a4..15c8c73331 100644
--- a/Documentation/admin-guide/thunderbolt.rst
+++ b/Documentation/admin-guide/thunderbolt.rst
@@ -296,6 +296,16 @@ information is missing.
To recover from this mode, one needs to flash a valid NVM image to the
host controller in the same way it is done in the previous chapter.
+When the NVM image is corrupted, certain host controllers will report
+an invalid Vendor ID preventing the module from exposing the nvm access
+nodes. If so, either load the thunderbolt module with option
+``switch_nvm_vendor_override=vendorID`` or add
+``thunderbolt.switch_nvm_vendor_override=vendorID`` to your boot
+parameters. You need to set ``vendorID`` to the appropriate value.
+On Intel systems, this is likely ``0x8086`` but you should verify this
+before doing anything as otherwise you may cause further damage to your
+controller.
+
Networking over Thunderbolt cable
---------------------------------
Thunderbolt technology allows software communication between two hosts