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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. The current TPM TIS driver only supports software detection of the wait signal. To support SPI controllers that use hardware to detect the wait signal, add the function tpm_tis_spi_transfer_half() and move the existing code for software based detection into a function called tpm_tis_spi_transfer_full(). SPI controllers that only support half-duplex transfers will always call tpm_tis_spi_transfer_half() because they cannot support software based detection. The bit SPI_TPM_HW_FLOW is set to indicate to the SPI controller that hardware detection is required and it is the responsibility of the SPI controller driver to determine if this is supported or not. For hardware flow control, CMD-ADDR-DATA messages are combined into a single message where as for software flow control exiting method of CMD-ADDR in a message and DATA in another is followed. [jarkko: Fixed the function names to match the code change, and the tag in the short summary.] Signed-off-by: Krishna Yarlagadda <kyarlagadda@nvidia.com> Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org> Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org> |
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.