From 5cc0101d1f88500f8901d01b035af743215d4c3a Mon Sep 17 00:00:00 2001 From: Peter Huewe Date: Thu, 2 Mar 2017 13:03:15 +0000 Subject: [PATCH] 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: Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy") Signed-off-by: Alexander Steffen Signed-off-by: Peter Huewe Reviewed-by: Jarkko Sakkinen Tested-by: Benoit Houyere Signed-off-by: Jarkko Sakkinen --- 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 3015c8b65f18..88fe72ae967f 100644 --- a/drivers/char/tpm/tpm_tis_spi.c +++ b/drivers/char/tpm/tpm_tis_spi.c @@ -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.len = transfer_len; + spi_xfer.delay_usecs = 5; if (direction) { spi_xfer.tx_buf = NULL; -- 2.20.1