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Date: Thu, 16 Feb 2017 21:09:42 -0800 From: Christophe Ricard <christophe.ricard@...il.com> To: Peter Huewe <peter.huewe@...ineon.com>, Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> Cc: Jason Gunthorpe <jgunthorpe@...idianresearch.com>, tpmdd-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org, peterhuewe@....de, Christophe Ricard <christophe-h.ricard@...com>, stable@...r.kernel.org, Alexander Steffen <Alexander.Steffen@...ineon.com> Subject: Re: [PATCH 5/5] tpm_tis_spi: Add small delay after last transfer Are you sure it is not better to introduce this delay directly in the rpi spi driver ? Other than that i don't see any issue with it. On 16/02/2017 08:09, Peter Huewe wrote: > 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@...r.kernel.org> > Fixes: 0edbfea537d1 ("tpm/tpm_tis_spi: Add support for spi phy") > Signed-off-by: Alexander Steffen <Alexander.Steffen@...ineon.com> > Signed-off-by: Peter Huewe <peter.huewe@...ineon.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 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;
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