AM6442: Writing to SWRV and KEYREV fuses in a Linux environment

Hello,

David Potts said:

Is that because they are not supported by the 'standard' SYSFW, or because it is left as an exercise for the reader ?

The standard SYSFW supports writing SWREV & KEYREV with the following TISCI APIs.

• https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/security/otp_revision.html#sec-api-wr-swrev-otp
• https://software-dl.ti.com/tisci/esd/latest/2_tisci_msgs/security/otp_revision.html#sec-api-wr-keyrev-otp

The Yocto implementation is missing for these because the writing requires 1.8V VPP supply which requires custom code as per the VPP enable schematic design of the board. If you already have a way to enable this 1.8V VPP one way or another then you may integrate these TISCI APIs in the OPTEE.

David Potts said:

Secondly, it is not clear if we can run the opt_keywriter from an image written to an SD-card, or if the identified boot devices (uart, usb, ospi, jtag) are the only ones that enables extra security to permit the fuses to be blown ?

The keywriter binary can be booted from any ROM supported boot media.

Regards,

Prashant

Many thanks, very helpful