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

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Message-ID: <5d430cfb.1c69fb81.9480d.0d81@mx.google.com>
Date:   Thu, 01 Aug 2019 09:02:02 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Alexander Steffen <Alexander.Steffen@...ineon.com>,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Peter Huewe <peterhuewe@....de>
Cc:     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

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.