linux-kernel - RE: [PATCH v2 0/2] char: tpm: add new driver for tpm i2c ptp

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Message-ID: <9c8e216dbc4f43dbaa1701dc166b05e0@NTILML02.nuvoton.com>
Date:   Thu, 18 Jul 2019 12:51:44 +0000
From:   <Eyal.Cohen@...oton.com>
To:     <jarkko.sakkinen@...ux.intel.com>, <tmaimon77@...il.com>
CC:     <oshrialkoby85@...il.com>, <Alexander.Steffen@...ineon.com>,
        <robh+dt@...nel.org>, <mark.rutland@....com>, <peterhuewe@....de>,
        <jgg@...pe.ca>, <arnd@...db.de>, <gregkh@...uxfoundation.org>,
        <oshri.alkoby@...oton.com>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-integrity@...r.kernel.org>,
        <gcwilson@...ibm.com>, <kgoldman@...ibm.com>,
        <nayna@...ux.vnet.ibm.com>, <Dan.Morav@...oton.com>,
        <oren.tanami@...oton.com>
Subject: RE: [PATCH v2 0/2] char: tpm: add new driver for tpm i2c ptp

Hi Jarkko and Alexander,

We have made an additional code review on the TPM TIS core driver, it looks quite good and we can connect our new I2C driver to this layer.
However, there are several differences between the SPI interface and the I2C interface that will require changes to the TIS core.
At a minimum we thought of:
1. Handling TPM Localities in I2C is different
2. Handling I2C CRC - relevant only to I2C bus hence not supported today by TIS core
3. Handling Chip specific issues, since I2C implementation might be slightly different across the various TPM vendors
4. Modify tpm_tis_send_data and tpm_tis_recv_data to work according the TCG Device Driver Guide (optimization on TPM_STS access and send/recv retry)
Besides this, during development we might encounter additional differences between SPI and I2C.

We currently target to allocate an eng. to work on this on the second half of August with a goal to have the driver ready for the next kernel merge window.

Regards,
Eyal.

-----Original Message-----
From: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
Sent: Monday, July 15, 2019 12:46 PM
To: Tomer Maimon <tmaimon77@...il.com>
Cc: Oshri Alkobi <oshrialkoby85@...il.com>; Alexander Steffen <Alexander.Steffen@...ineon.com>; Rob Herring <robh+dt@...nel.org>; Mark Rutland <mark.rutland@....com>; peterhuewe@....de; jgg@...pe.ca; Arnd Bergmann <arnd@...db.de>; Greg KH <gregkh@...uxfoundation.org>; IS20 Oshri Alkoby <oshri.alkoby@...oton.com>; devicetree <devicetree@...r.kernel.org>; AP MS30 Linux Kernel community <linux-kernel@...r.kernel.org>; linux-integrity@...r.kernel.org; gcwilson@...ibm.com; kgoldman@...ibm.com; nayna@...ux.vnet.ibm.com; IS30 Dan Morav <Dan.Morav@...oton.com>; IS20 Eyal Cohen <Eyal.Cohen@...oton.com>
Subject: Re: [PATCH v2 0/2] char: tpm: add new driver for tpm i2c ptp

On Mon, Jul 15, 2019 at 11:08:47AM +0300, Tomer Maimon wrote:
>    Thanks for your feedback and sorry for the late response.
>
>    Due to the amount of work required to handle this technical feedback and
>    project constraints we need to put this task on hold for the near future.
>
>    In the meantime, anyone from the community is welcome to take over this
>    code and handle the re-design for the benefit of the entire TPM community.

Ok, so there is already driver for this called tpm_tis_core.

So you go and create a new module, whose name given the framework of things that we already have deployed, is destined to be tpm_tis_i2c.

Then you roughly implement a new physical layer by using  a callback interface provided to you by tpm_tis_core.

The so called re-design was already addressed by Alexander [1].

How hard can it be seriously?

[1] https://urldefense.proofpoint.com/v2/url?u=https-3A__lkml.org_lkml_2019_7_4_331&d=DwIBAg&c=ue8mO8zgC4VZ4q_aNVKt8G9MC01UFDmisvMR1k-EoDM&r=hjzIxEsS8wf3Ezr__r0ZOjw3kki8jIlQK-SQ5pWhXaM&m=aYs86sTFmxqvlI5rE2AWLGRl0lb9XRuiRKVtsCaXdRM&s=_3MMoq5UISFwMfK4OfgLbA2kMfZVgEfgkaWKqDEUXGw&e=

/Jarkko

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