From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarkko Sakkinen Subject: Re: [PATCH RESEND v3 0/2] tpm_tis_spi: Use DMA-safe memory Date: Sat, 2 Sep 2017 13:54:24 +0300 Message-ID: <20170902105424.ej67umlzqfgaue7x@linux.intel.com> References: <20170831165819.13544-1-Alexander.Steffen@infineon.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170831165819.13544-1-Alexander.Steffen@infineon.com> Sender: owner-linux-security-module@vger.kernel.org To: Alexander Steffen Cc: tpmdd-devel@lists.sourceforge.net, benoit.houyere@st.com, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org List-Id: tpmdd-devel@lists.sourceforge.net 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