On Thu, Feb 16, 2017 at 04:09:46PM +0000, Peter Huewe wrote: > 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@xxxxxxxxxxxxxxx> > Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy") > Signed-off-by: Alexander Steffen <Alexander.Steffen@xxxxxxxxxxxx> > Signed-off-by: Peter Huewe <peter.huewe@xxxxxxxxxxxx> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx> /Jarkko > --- > drivers/char/tpm/tpm_tis_spi.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/drivers/char/tpm/tpm_tis_spi.c b/drivers/char/tpm/tpm_tis_spi.c > index b50c5b072df3..685c51bf5d7e 100644 > --- a/drivers/char/tpm/tpm_tis_spi.c > +++ b/drivers/char/tpm/tpm_tis_spi.c > @@ -110,6 +110,7 @@ static int tpm_tis_spi_transfer(struct tpm_tis_data *data, u32 addr, u8 len, > > spi_xfer.cs_change = 0; > spi_xfer.len = transfer_len; > + spi_xfer.delay_usecs = 5; > > if (direction) { > spi_xfer.tx_buf = NULL; > -- > 2.7.4 >