Re: [PATCH v2 5/6] tpm: add driver for cr50 on SPI

[Alexander Steffen]

On 18.07.2019 20:11, Stephen Boyd wrote:
> Quoting Alexander Steffen (2019-07-18 09:47:22)
> > On 17.07.2019 23:38, Stephen Boyd wrote:
> > > Quoting Stephen Boyd (2019-07-17 12:57:34)
> > > > Quoting Alexander Steffen (2019-07-17 05:00:06)
> > > > > Can't the code be shared more explicitly, e.g. by cr50_spi wrapping
> > > > > tpm_tis_spi, so that it can intercept the calls, execute the additional
> > > > > actions (like waking up the device), but then let tpm_tis_spi do the
> > > > > common work?
> > > >
> > > > I suppose the read{16,32} and write32 functions could be reused. I'm not
> > > > sure how great it will be if we combine these two drivers, but I can
> > > > give it a try today and see how it looks.
> > >
> > > Here's the patch. I haven't tested it besides compile testing.
>
> The code seems to work but I haven't done any extensive testing besides
> making sure that the TPM responds to pcr reads and some commands like
> reading random numbers.
>
> > Thanks for providing this. Makes it much easier to see what the actual
> > differences between the devices are.
> >
> > Do we have a general policy on how to support devices that are very
> > similar but need special handling in some places? Not duplicating the
> > whole driver just to change a few things definitely seems like an
> > improvement (and has already been done in the past, as with
> > TPM_TIS_ITPM_WORKAROUND). But should all the code just be added to
> > tpm_tis_spi.c? Or is there some way to keep a clearer separation,
> > especially when (in the future) we have multiple devices that all have
> > their own set of deviations from the spec?
>
> If you have any ideas on how to do it please let me know. At this point,
> I'd prefer if the maintainers could provide direction on what they want.

Sure, I'd expect Jarkko will say something once he's back from vacation.

Alexander