linux-kernel - Re: [Patch V10 0/3] Tegra TPM driver with HW flow control

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Date:   Fri, 21 Apr 2023 05:50:13 -0700
From:   Jerry Snitselaar <jsnitsel@...hat.com>
To:     Krishna Yarlagadda <kyarlagadda@...dia.com>
Cc:     robh+dt@...nel.org, broonie@...nel.org, peterhuewe@....de,
        jgg@...pe.ca, jarkko@...nel.org, 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 V10 0/3] Tegra TPM driver with HW flow control

On Fri, Apr 21, 2023 at 02:43:06PM +0530, Krishna Yarlagadda wrote:
> TPM devices may insert wait state on last clock cycle of ADDR phase.
> For SPI controllers that support full-duplex transfers, this can be
> detected using software by reading the MISO line. For SPI controllers
> that only support half-duplex transfers, such as the Tegra QSPI, it is
> not possible to detect the wait signal from software. The QSPI
> controller in Tegra234 and Tegra241 implement hardware detection of the
> wait signal which can be enabled in the controller for TPM devices.
> 
> Add HW flow control in TIS driver and a flag in SPI data to indicate
> wait detection is required in HW. SPI controller driver determines if
> this is supported. Add HW detection in Tegra QSPI controller.
> 
> Updates in this patch set 
>  - 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.
> 
> V10
>  - use spi_sync in place of spi_sync_locked
> V9
>  - renamed tpm spi transfer functions
> V8:
>  - fix compile warning.
> V7:
>  - updated patch description.
>  - TPM flag set in probe.
>  - minor comments.
> V6:
>  - Fix typo in chip name Tegra234.
>  - Debug logs change skipped to be sent later.
>  - Consistent usage of soc flag.
> 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: Add hardware wait polling
>   spi: tegra210-quad: Enable TPM wait polling
> 
>  drivers/char/tpm/tpm_tis_spi_main.c | 91 ++++++++++++++++++++++++++++-
>  drivers/spi/spi-tegra210-quad.c     | 14 +++++
>  include/linux/spi/spi.h             | 16 ++++-
>  3 files changed, 116 insertions(+), 5 deletions(-)
> 
> -- 
> 2.17.1
> 

Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>