From: Peter Huewe <peter.huewe@infineon.com> To: <tpmdd-devel@lists.sourceforge.net> Cc: Peter Huewe <peter.huewe@infineon.com>, <stable@vger.kernel.org>, Alexander Steffen <Alexander.Steffen@infineon.com>, Peter Huewe <peterhuewe@gmx.de>, Marcel Selhorst <tpmdd@selhorst.net>, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>, Jason Gunthorpe <jgunthorpe@obsidianresearch.com>, <linux-kernel@vger.kernel.org> Subject: [PATCH v2 5/5] tpm_tis_spi: Add small delay after last transfer Date: Thu, 2 Mar 2017 13:03:15 +0000 [thread overview] Message-ID: <1488459879-24349-6-git-send-email-peter.huewe@infineon.com> (raw) In-Reply-To: <1488459879-24349-1-git-send-email-peter.huewe@infineon.com> 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@vger.kernel.org> Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy") Signed-off-by: Alexander Steffen <Alexander.Steffen@infineon.com> Signed-off-by: Peter Huewe <peter.huewe@infineon.com> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com> Tested-by: Benoit Houyere <benoit.houyere@st.com> --- 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; -- 2.7.4
WARNING: multiple messages have this Message-ID (diff)
From: Peter Huewe <peter.huewe-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org> To: tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Peter Huewe <peter.huewe-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org> Subject: [PATCH v2 5/5] tpm_tis_spi: Add small delay after last transfer Date: Thu, 2 Mar 2017 13:03:15 +0000 [thread overview] Message-ID: <1488459879-24349-6-git-send-email-peter.huewe@infineon.com> (raw) In-Reply-To: <1488459879-24349-1-git-send-email-peter.huewe-d0qZbvYSIPpWk0Htik3J/w@public.gmane.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: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org> Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy") Signed-off-by: Alexander Steffen <Alexander.Steffen-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org> Signed-off-by: Peter Huewe <peter.huewe-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> Tested-by: Benoit Houyere <benoit.houyere-qxv4g6HH51o@public.gmane.org> --- 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; -- 2.7.4 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, SlashDot.org! http://sdm.link/slashdot
next prev parent reply other threads:[~2017-03-02 13:10 UTC|newest] Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-02 13:03 [PATCH v2 0/5] Fix whole native SPI TPM driver Peter Huewe 2017-03-02 13:03 ` [PATCH v2 1/5] tpm_tis_spi: Use single function to transfer data Peter Huewe 2017-03-02 13:03 ` Peter Huewe 2017-03-02 13:03 ` [PATCH v2 2/5] tpm_tis_spi: Abort transfer when too many wait states are signaled Peter Huewe 2017-03-02 13:03 ` Peter Huewe 2017-03-02 13:03 ` [PATCH v2 3/5] tpm_tis_spi: Check correct byte for wait state indicator Peter Huewe 2017-03-02 13:03 ` Peter Huewe 2017-03-02 13:03 ` [PATCH v2 4/5] tpm_tis_spi: Remove limitation of transfers to MAX_SPI_FRAMESIZE bytes Peter Huewe 2017-03-02 13:03 ` Peter Huewe 2017-03-02 13:03 ` Peter Huewe [this message] 2017-03-02 13:03 ` [PATCH v2 5/5] tpm_tis_spi: Add small delay after last transfer Peter Huewe [not found] ` <1488459879-24349-1-git-send-email-peter.huewe-d0qZbvYSIPpWk0Htik3J/w@public.gmane.org> 2017-03-06 21:10 ` [PATCH v2 0/5] Fix whole native SPI TPM driver Jarkko Sakkinen
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