linux-kernel - Re: [Patch V5 0/3] Tegra TPM driver with HW flow control

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Date:   Tue, 28 Feb 2023 04:28:06 +0200
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Krishna Yarlagadda <kyarlagadda@...dia.com>
Cc:     robh+dt@...nel.org, broonie@...nel.org, peterhuewe@....de,
        jgg@...pe.ca, krzysztof.kozlowski+dt@...aro.org,
        linux-spi@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        thierry.reding@...il.com, jonathanh@...dia.com,
        skomatineni@...dia.com, ldewangan@...dia.com
Subject: Re: [Patch V5 0/3] Tegra TPM driver with HW flow control

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