From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754173AbdIFMzE (ORCPT ); Wed, 6 Sep 2017 08:55:04 -0400 Received: from mga03.intel.com ([134.134.136.65]:32964 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753484AbdIFMzC (ORCPT ); Wed, 6 Sep 2017 08:55:02 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.41,484,1498546800"; d="scan'208";a="1011525043" Date: Wed, 6 Sep 2017 15:54:58 +0300 From: Jarkko Sakkinen To: Alexander Steffen Cc: tpmdd-devel@lists.sourceforge.net, benoit.houyere@st.com, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH RESEND v3 0/2] tpm_tis_spi: Use DMA-safe memory Message-ID: <20170906125458.ueqpmokh7bg64olc@linux.intel.com> References: <20170831165819.13544-1-Alexander.Steffen@infineon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170831165819.13544-1-Alexander.Steffen@infineon.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 > Applied to my bleeding edge master brach for more convenient testing. Have not yet applied to my next branch. /Jarkko