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

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Date:   Fri, 02 Aug 2019 18:21:06 +0300
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     Stephen Boyd <swboyd@...omium.org>,
        Alexander Steffen <Alexander.Steffen@...ineon.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

On Thu, 2019-08-01 at 09:02 -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.

Hi, I'm back. If there are already like obvious changes, please send an
update and I'll take a look at that.

/Jarkko