4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Peter Huewe <[email protected]> commit 5cc0101d1f88500f8901d01b035af743215d4c3a upstream. 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. Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy") Signed-off-by: Alexander Steffen <[email protected]> Signed-off-by: Peter Huewe <[email protected]> Reviewed-by: Jarkko Sakkinen <[email protected]> Tested-by: Benoit Houyere <[email protected]> Signed-off-by: Jarkko Sakkinen <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- drivers/char/tpm/tpm_tis_spi.c | 1 + 1 file changed, 1 insertion(+) --- a/drivers/char/tpm/tpm_tis_spi.c +++ b/drivers/char/tpm/tpm_tis_spi.c @@ -112,6 +112,7 @@ static int tpm_tis_spi_transfer(struct t spi_xfer.cs_change = 0; spi_xfer.len = transfer_len; + spi_xfer.delay_usecs = 5; if (direction) { spi_xfer.tx_buf = NULL;
