Date:   Tue, 28 Feb 2023 04:28:06 +0200
From:   Jarkko Sakkinen <jarkko@kernel.org>
To:     Krishna Yarlagadda <kyarlagadda@nvidia.com>
Cc:     robh+dt@kernel.org, broonie@kernel.org, peterhuewe@gmx.de,
        jgg@ziepe.ca, krzysztof.kozlowski+dt@linaro.org,
        linux-spi@vger.kernel.org, linux-tegra@vger.kernel.org,
        linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org,
        thierry.reding@gmail.com, jonathanh@nvidia.com,
        skomatineni@nvidia.com, ldewangan@nvidia.com
Subject: Re: [Patch V5 0/3] Tegra TPM driver with HW flow control
Message-ID: <Y/1mtnSAg0TrVH2H@kernel.org>
References: <20230227120702.13180-1-kyarlagadda@nvidia.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20230227120702.13180-1-kyarlagadda@nvidia.com>
Precedence: bulk

On Mon, Feb 27, 2023 at 05:36:59PM +0530, Krishna Yarlagadda wrote:
> TPM interface spec defines flow control where TPM device would drive
> MISO at same cycle as last address bit sent by controller on MOSI. This
> state of wait can be detected by software reading the MISO line or
> by controller hardware. Support sending transfers to controller in
> single message and handle flow control in hardware. Half duplex
> controllers have to support flow control in hardware.
> 
> Tegra234 and Tegra241 chips have QSPI controller that supports TPM
> Interface Specification (TIS) flow control.
> Since the controller only supports half duplex, SW wait polling
> (flow control using full duplex transfers) method implemented in
> tpm_tis_spi_main.c will not work and have to us HW flow control.
> 
> Updates in this patchset 
>  - Tegra QSPI identifies itself as half duplex.
>  - TPM TIS SPI driver skips flow control for half duplex and send
>    transfers in single message for controller to handle it.
>  - TPM device identifies as TPM device for controller to detect and
>    enable HW TPM wait poll feature.
> 
> Verified with a TPM device on Tegra241 ref board using TPM2 tools.
> 
> V5:
>  - No SPI bus locking.
> V4:
>  - Split api change to different patch.
>  - Describe TPM HW flow control.
> V3:
>  - Use SPI device mode flag and SPI controller flags.
>  - Drop usage of device tree flags.
>  - Generic TPM half duplex controller handling.
>  - HW & SW flow control for TPM. Drop additional driver.
> V2:
>  - Fix dt schema errors.
> 
> Krishna Yarlagadda (3):
>   spi: Add TPM HW flow flag
>   tpm_tis-spi: Support hardware wait polling
>   spi: tegra210-quad: Enable TPM wait polling
> 
>  drivers/char/tpm/tpm_tis_spi_main.c | 92 ++++++++++++++++++++++++++++-
>  drivers/spi/spi-tegra210-quad.c     | 21 +++++++
>  include/linux/spi/spi.h             |  7 ++-
>  3 files changed, 115 insertions(+), 5 deletions(-)
> 
> -- 
> 2.17.1
> 

Funny that this is already in v5, I'm seeing this for the very first time.

BR, Jarkko