Re: tpm: SLM9670 does not work on T1023

[Jarkko Sakkinen <jarkko@kernel.org>]

On Sun, Sep 14, 2025 at 08:06:15PM +0300, Jarkko Sakkinen wrote:
> 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 :-)

Ugh, no. Probably it is device tree given false data. I recall we have
some ways to override device tree, so find the data sheet for the TPM
and rewrite the ids I suppose.

BR, Jarkko