linux-kernel - Re: [PATCH v6] char: tpm: add i2c driver for cr50

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Message-ID: <20201211103443.GA12091@kernel.org>
Date:   Fri, 11 Dec 2020 12:34:43 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Adrian Ratiu <adrian.ratiu@...labora.com>
Cc:     linux-integrity@...r.kernel.org, Peter Huewe <peterhuewe@....de>,
        Jason Gunthorpe <jgg@...pe.ca>, linux-kernel@...r.kernel.org,
        kernel@...labora.com,
        "dlaurie@...omium.org" <dlaurie@...omium.org>,
        Helen Koike <helen.koike@...labora.com>,
        Ezequiel Garcia <ezequiel@...labora.com>
Subject: Re: [PATCH v6] char: tpm: add i2c driver for cr50

On Wed, Dec 09, 2020 at 02:41:45PM +0200, Adrian Ratiu wrote:
> On Tue, 08 Dec 2020, Jarkko Sakkinen <jarkko@...nel.org> wrote:
> > On Mon, Dec 07, 2020 at 04:20:16PM +0200, Adrian Ratiu wrote:
> > > From: "dlaurie@...omium.org" <dlaurie@...omium.org>  Add TPM 2.0
> > > compatible I2C interface for chips with cr50 firmware. The firmware
> > > running on the currently supported H1 MCU requires a special driver
> > > to handle its specific protocol, and this makes it unsuitable to use
> > > tpm_tis_core_* and instead it must implement the underlying TPM
> > > protocol similar to the other I2C TPM drivers.   - All 4 bytes of
> > > status register must be read/written at once.  - FIFO and burst
> > > count is limited to 63 and must be drained by AP.  - Provides an
> > > interrupt to indicate when read response data is ready and when the
> > > TPM is finished processing write data.   This driver is based on the
> > > existing infineon I2C TPM driver, which most closely matches the
> > > cr50 i2c protocol behavior.
> > 
> > Starts to look legit. Has anyone tested this?
> 
> I tested on an x86_64 Chromebook EVE (aka Google Pixelbook) by chainloading
> in legacy mode and booting into a Yocto-based userspace (meta-chromebook)
> where I used tpm2-tools to communicate with the chip and also built and
> tested a ChromiumOS userspace in developer mode.
> 
> I do not have access to other HW which has this chip, so it is about as much
> testing I can do to confirm the driver works on this HW.
> 
> Adrian

So can you respond to this with tested-by. It's sufficient because
collateral effects of driver failing are insignificant for the kernel
as whole.
 
 /Jarkko