Re: [PATCH v7 4/6] tpm: tpm_tis_spi: Support cr50 devices

From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Stephen Boyd <swboyd@chromium.org>
Cc: Peter Huewe <peterhuewe@gmx.de>,
	Andrey Pronin <apronin@chromium.org>,
	linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org,
	Duncan Laurie <dlaurie@chromium.org>,
	Jason Gunthorpe <jgg@ziepe.ca>, Arnd Bergmann <arnd@arndb.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Guenter Roeck <groeck@chromium.org>,
	Alexander Steffen <Alexander.Steffen@infineon.com>,
	Heiko Stuebner <heiko@sntech.de>
Subject: Re: [PATCH v7 4/6] tpm: tpm_tis_spi: Support cr50 devices
Date: Mon, 7 Oct 2019 01:32:28 +0300	[thread overview]
Message-ID: <20191006223228.GA8860@linux.intel.com> (raw)
In-Reply-To: <20190920183240.181420-5-swboyd@chromium.org>

On Fri, Sep 20, 2019 at 11:32:38AM -0700, Stephen Boyd wrote:
> From: Andrey Pronin <apronin@chromium.org>
> 
> Add TPM2.0 PTP FIFO compatible SPI interface for chips with Cr50
> firmware. The firmware running on the currently supported H1 Secure
> Microcontroller requires a special driver to handle its specifics:
> 
>  - need to ensure a certain delay between SPI transactions, or else
>    the chip may miss some part of the next transaction
>  - if there is no SPI activity for some time, it may go to sleep,
>    and needs to be waken up before sending further commands
>  - access to vendor-specific registers
> 
> Cr50 firmware has a requirement to wait for the TPM to wakeup before
> sending commands over the SPI bus. Otherwise, the firmware could be in
> deep sleep and not respond. The method to wait for the device to wakeup
> is slightly different than the usual flow control mechanism described in
> the TCG SPI spec. Add a completion to tpm_tis_spi_transfer() before we
> start a SPI transfer so we can keep track of the last time the TPM
> driver accessed the SPI bus to support the flow control mechanism.
> 
> Split the cr50 logic off into a different file to keep it out of the
> normal code flow of the existing SPI driver while making it all part of
> the same module when the code is optionally compiled into the same
> module. Export a new function, tpm_tis_spi_init(), and the associated
> read/write/transfer APIs so that we can do this. Make the cr50 code wrap
> the tpm_tis_spi_phy struct with its own struct to override the behavior
> of tpm_tis_spi_transfer() by supplying a custom flow control hook. This
> shares the most code between the core driver and the cr50 support
> without combining everything into the core driver or exporting module
> symbols.
> 
> Signed-off-by: Andrey Pronin <apronin@chromium.org>
> Cc: Andrey Pronin <apronin@chromium.org>
> Cc: Duncan Laurie <dlaurie@chromium.org>
> Cc: Jason Gunthorpe <jgg@ziepe.ca>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Guenter Roeck <groeck@chromium.org>
> Cc: Alexander Steffen <Alexander.Steffen@infineon.com>
> Cc: Heiko Stuebner <heiko@sntech.de>

First, I apologize for such a long latency (two weeks).

I think this looks legit now.

Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

/Jarkko