This is a note to let you know that I've just added the patch titled
tpm_tis_spi: Add small delay after last transfer
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tpm_tis_spi-add-small-delay-after-last-transfer.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 5cc0101d1f88500f8901d01b035af743215d4c3a Mon Sep 17 00:00:00 2001
From: Peter Huewe <peter.huewe@xxxxxxxxxxxx>
Date: Thu, 2 Mar 2017 13:03:15 +0000
Subject: tpm_tis_spi: Add small delay after last transfer
From: Peter Huewe <peter.huewe@xxxxxxxxxxxx>
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 <Alexander.Steffen@xxxxxxxxxxxx>
Signed-off-by: Peter Huewe <peter.huewe@xxxxxxxxxxxx>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Tested-by: Benoit Houyere <benoit.houyere@xxxxxx>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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;
Patches currently in stable-queue which might be from peter.huewe@xxxxxxxxxxxx are
queue-4.9/tpm_tis_spi-abort-transfer-when-too-many-wait-states-are-signaled.patch
queue-4.9/tpm_tis_spi-remove-limitation-of-transfers-to-max_spi_framesize-bytes.patch
queue-4.9/tpm_tis_core-choose-appropriate-timeout-for-reading-burstcount.patch
queue-4.9/tpm_tis_spi-add-small-delay-after-last-transfer.patch
queue-4.9/tpm_tis_spi-check-correct-byte-for-wait-state-indicator.patch
queue-4.9/tpm_tis_spi-use-single-function-to-transfer-data.patch