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: 0edbfea537 ("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>
The algorithm for sending data to the TPM is mostly identical to the
algorithm for receiving data from the TPM, so a single function is
sufficient to handle both cases.
This is a prequisite for all the other fixes, so we don't have to fix
everything twice (send/receive)
v2: u16 instead of u8 for the length.
Cc: <stable@vger.kernel.org>
Fixes: 0edbfea537 ("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>
