Commit 5cc0101d authored by Peter Huewe's avatar Peter Huewe Committed by Jarkko Sakkinen

tpm_tis_spi: Add small delay after last transfer

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: 0edbfea5 ("tpm/tpm_tis_spi: Add support for spi phy")
Signed-off-by: default avatarAlexander Steffen <Alexander.Steffen@infineon.com>
Signed-off-by: default avatarPeter Huewe <peter.huewe@infineon.com>
Reviewed-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: default avatarBenoit Houyere <benoit.houyere@st.com>
Signed-off-by: default avatarJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
parent 591e48c2
...@@ -111,6 +111,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len, ...@@ -111,6 +111,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u16 len,
spi_xfer.cs_change = 0; spi_xfer.cs_change = 0;
spi_xfer.len = transfer_len; spi_xfer.len = transfer_len;
spi_xfer.delay_usecs = 5;
if (direction) { if (direction) {
spi_xfer.tx_buf = NULL; spi_xfer.tx_buf = NULL;
......
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