From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932882AbdBPQKc (ORCPT ); Thu, 16 Feb 2017 11:10:32 -0500 Received: from smtp2.infineon.com ([217.10.52.18]:52004 "EHLO smtp2.infineon.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932359AbdBPQKa (ORCPT ); Thu, 16 Feb 2017 11:10:30 -0500 X-SBRS: None From: Peter Huewe To: Jarkko Sakkinen CC: Jason Gunthorpe , , , , Christophe Ricard , "Peter Huewe" , , Alexander Steffen Subject: [PATCH 5/5] tpm_tis_spi: Add small delay after last transfer Date: Thu, 16 Feb 2017 16:09:46 +0000 Message-ID: <1487261386-2641-5-git-send-email-peter.huewe@infineon.com> X-Mailer: git-send-email 2.7.4 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [172.29.170.145] X-ClientProxiedBy: MUCSE601.infineon.com (172.23.7.102) To MUCSE612.infineon.com (172.23.7.113) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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