From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Edworthy Subject: Question about dma-ranges property for PCI host controllers Date: Thu, 11 Aug 2016 15:00:42 +0000 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 8BIT Return-path: Content-Language: en-US Sender: linux-pci-owner@vger.kernel.org To: "linux-pci@vger.kernel.org" Cc: "linux-renesas-soc@vger.kernel.org" , "devicetree@vger.kernel.org" List-Id: devicetree@vger.kernel.org Hi, A few PCI host controllers use the "dma-ranges" property to specify the mapping from PCI bus addresses to physical addresses. In the case of R-Car PCIe Host controllers, the intention was to set this property as a 1 to 1 mapping for all DDR that could be addressed by the device. However, there are some limitations for the R-Car controller which meant that we could only map a subset of the DDR range - this limitation has prompted us to work on enabling the IOMMU behind the PCI controller. When there is an IOMMU behind the PCI controller, the "dma-ranges" property specifies the mapping from PCI bus addresses to an IOVA address. So should the property map all address space? Note that this is not actually possible with the R-Car hardware, but I found that the IOVA address space is outside of the DDR address space that we were using so had change it. Thanks Phil