Hello Lino, hello Lukas, On Tue, Sep 26, 2023 at 09:09:36PM +0200, Lukas Wunner wrote: > From: Lino Sanfilippo <l.sanfilippo@xxxxxxxxxx> > > Normally the platform firmware is responsible for taking a Trusted > Platform Module out of reset on boot and storing measurements into it. > > However if the platform firmware is incapable of doing that -- as is the > case on the Raspberry Pi -- then the onus is on the kernel to take the > TPM out of reset before trying to attach a driver to it. > > Provide a reset driver for such platforms. > > The Infineon SLB9670 TPM requires a specific reset sequence on its RST# > pin which is documented in sections 5.4 and 5.5 of the datasheet: > > https://www.infineon.com/dgdl/Infineon-SLB%209670VQ2.0-DataSheet-v01_04-EN.pdf?fileId=5546d4626fc1ce0b016fc78270350cd6 > > The sequence with minimum wait intervals is as follows: > > deassert RST# > wait at least 60 ms > assert RST# > wait at least 2 usecs > deassert RST# > wait at least 60 ms > assert RST# > wait at least 2 usecs > deassert RST# > wait at least 60 ms before issuing the first TPM command Are you really sure that this change is required? I have seen the RST# Timing diagram in the datasheet, however I wonder if a reset is required at all during power-up, for example. Not to mention that I would have expected some firmware to implement such reset timing and I was not able to find any (I looked at arm/arm64), if this is really required I the driver can work at all? Which platform firmware implements such reset sequence? Not to mention that I was able to see the driver probe succeed in a similar setup to the one you are describing in the commit message (different board, arm64, but nothing done by the platform firmware). What am I missing? Thanks, Francesco
