Patch "tpm_tis_spi: Add small delay after last transfer" has been added to the 4.9-stable tree

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 <[email protected]> know about it.

From: Peter Huewe <[email protected]>
Date: Thu, 2 Mar 2017 13:03:15 +0000
Subject: tpm_tis_spi: Add small delay after last transfer

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.

---
 drivers/char/tpm/tpm_tis_spi.c |    1 +
 1 file changed, 1 insertion(+)

@@ -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 [email protected] 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