From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Steffen Subject: [PATCH v3 0/2] tpm_tis_spi: Use DMA-safe memory Date: Thu, 24 Aug 2017 10:27:43 +0200 Message-ID: <20170824082745.9372-1-Alexander.Steffen@infineon.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: tpmdd-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org To: jarkko.sakkinen-VuQAYsv1563Yd54FQh9/CA@public.gmane.org, tpmdd-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: tpmdd-devel@lists.sourceforge.net 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 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot