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

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Date:   Fri, 2 Aug 2019 22:43:24 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Alexander Steffen <Alexander.Steffen@...ineon.com>,
        Peter Huewe <peterhuewe@....de>,
        Andrey Pronin <apronin@...omium.org>,
        linux-kernel@...r.kernel.org, Jason Gunthorpe <jgg@...pe.ca>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-integrity@...r.kernel.org,
        Duncan Laurie <dlaurie@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH v2 5/6] tpm: add driver for cr50 on SPI

On Thu, Aug 01, 2019 at 09:02:02AM -0700, Stephen Boyd wrote:
> Quoting Alexander Steffen (2019-07-19 00:53:00)
> > 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.
> > 
> 
> Should I just resend this patch series? I haven't attempted to make the
> i2c driver changes, but at least the SPI driver changes seem good enough
> to resend.

Go ahead.

/Jarkko