5cc0101d1f
Testing the implementation with a Raspberry Pi 2 showed that under some
circumstances its SPI master erroneously releases the CS line before the
transfer is complete, i.e. before the end of the last clock. In this case
the TPM ignores the transfer and misses for example the GO command. The
driver is unable to detect this communication problem and will wait for a
command response that is never going to arrive, timing out eventually.
As a workaround, the small delay ensures that the CS line is held long
enough, even with a faulty SPI master. Other SPI masters are not affected,
except for a negligible performance penalty.
Cc: <stable@vger.kernel.org>
Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy")
Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com>
Signed-off-by: Peter Huewe <peter.huewe@infineon.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Benoit Houyere <benoit.houyere@st.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. 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.