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Date: Sat, 2 Sep 2017 13:54:24 +0300 From: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com> To: Alexander Steffen <Alexander.Steffen@...ineon.com> Cc: tpmdd-devel@...ts.sourceforge.net, benoit.houyere@...com, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org Subject: Re: [PATCH RESEND v3 0/2] tpm_tis_spi: Use DMA-safe memory On Thu, Aug 31, 2017 at 06:58:17PM +0200, Alexander Steffen wrote: > The documentation says that DMA-safe memory is required for SPI transfers. > The I/O buffers passed in by the caller can be allocated anywhere, > including on the stack, which is not DMA-safe. So the data needs to be > copied to separate, DMA-safe buffers. > > We did not see any DMA-related issues on our test systems, even without > DMA-safe buffers. But this might simply be due to the fact that the SPI > transfer size is rather small, so our systems do not bother to set up DMA > transfers. Other systems might do so. > > v2: > - Updated commit message with more explanations. > > v3: > - Split into two patches, one for making the buffers DMA-safe and another > for using only a single buffer. > > Alexander Steffen (2): > tpm_tis_spi: Use DMA-safe memory for SPI transfers > tpm_tis_spi: Use a single buffer for SPI transfers > > drivers/char/tpm/tpm_tis_spi.c | 32 ++++++++++++++++++-------------- > 1 file changed, 18 insertions(+), 14 deletions(-) > > -- > 2.7.4 > Great, I'll try to get means to test this! /Jarkko
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