SPI0 support for TPM

The PCH’s SPI0 flash controller supports a discrete TPM on the platform via its dedicated SPI0_​CS2# signal. The platform must have no more than 1 TPM.

SPI0 controller supports accesses to SPI0 TPM at approximately 14 MHz, 33 MHz and 50 MHz depending on the PCH soft strap. 20 MHz is the reset default, a valid PCH soft strap setting overrides the requirement for the 20 MHz. SPI0 TPM device must support a clock of 20 MHz, and thus should handle 15-20 MHz. It may but is not required to support a frequency greater than 20 MHz.

TPM requires the support for the interrupt routing. However, the TPM’s interrupt pin is routed to the PCH's interrupt configurable GPIO pin. Thus, TPM interrupt is completely independent from the SPI0 controller.