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eac9347d93
During flow control we are just reading from the TPM, yet our spi_xfer has the tx_buf and rx_buf both non-NULL which means we're requesting a full duplex transfer. SPI is always somewhat of a full duplex protocol anyway and in theory the other side shouldn't really be looking at what we're sending it during flow control, but it's still a bit ugly to be sending some "random" data when we shouldn't. The default tpm_tis_spi_flow_control() tries to address this by setting 'phy->iobuf[0] = 0'. This partially avoids the problem of sending "random" data, but since our tx_buf and rx_buf both point to the same place I believe there is the potential of us sending the TPM's previous byte back to it if we hit the retry loop. Another flow control implementation, cr50_spi_flow_control(), doesn't address this at all. Let's clean this up and just make the tx_buf NULL before we call flow_control(). Not only does this ensure that we're not sending any "random" bytes but it also possibly could make the SPI controller behave in a slightly more optimal way. NOTE: no actual observed problems are fixed by this patch--it's was just made based on code inspection. Signed-off-by: Douglas Anderson <dianders@chromium.org> Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
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
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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.