Re: tpm: SLM9670 does not work on T1023

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Sep 11, 2025 at 03:52:33PM +0200, Alexander Wilhelm wrote:
> Hello devs,
> 
> I'm trying to bring up the SLM9670 TPM 2.0 device connected via SPI on a QorIQ
> T1023-based board. Pin control is fully configured through the RCW, so I haven't
> added any additional properties in the device tree. The SPI controller accesses
> the TPM using `#CS0`.
> 
> However, the driver reads an incorrect vendor ID (0x1000000) and hangs during
> the startup sequence. A logic analyzer shows that the chip select line goes high
> immediately after transmitting 4 bytes, which, according to various forum
> discussions, does not comply with the TPM specification. Unfortunately, I
> haven't found a definitive solution to this issue.

So, at least the vendor ID is bogus meaning that TPM driver is doing
right thing.

> 
> Could this be a bug in the `spi-fsl-espi` driver, or is it possibly a hardware
> limitation of the T1023? I've come across some suggestions that involve using a
> GPIO as an alternative chip select instead of the one provided by the SPI
> controller. Can anyone confirm whether this workaround is viable? I’d prefer to
> avoid a PCB redesign unless it's absolutely necessary.

My first guess would be that the firmware inside TPM actually does throw
a broken vendor ID but it is exactly a guess :-)

I'll follow this, and please cc me also to future threads but right now
I'm clueless.

> 
> 
> Best regards
> Alexander Wilhelm


BR, Jarkko