I had written the driver in C for my PCICard where i used I/O Mapping.Now
i want to use the same driver for PCIEXPRESS card using Memory Mapping.
Can any one Suggest me how to do it?
Related
I am trying to use DMA to transfer data from an SSD drive (PCIe device) to an AXI4 stream peripheral e.g., a FIFO implemented on FPGA. DDR memory is not involved in the transaction. PCIe is implemented using the AXI Memory Mapped to PCI Express (2.9) IP and configured as root complex in Vivado. The block design was created based on the following tutorial (the only difference being that a DMA was used instead of a CDMA): https://www.fpgadeveloper.com/2016/04/zynq-pci-express-root-complex-design-in-vivado.html/
As can be seen in the Address Editor, the DMA can access the PCIe and PS address spaces. My user-space driver fails when it uses a PCIe address (BAR0) as source address for the transaction, so that's probably not the right way for DMA transactions over PCIe link. There's not much information online about this topic.
I'm using Vivado 2018.3 and a Zynq-7000 device, part xc7z030sbg485-1.
Does anyone know the right way of using DMA to perform data transfers over the PCIe link?
Please let me know if you need any clarification.
Thank you.
hw_design
hw_design_address_editor
I'm a software developer but I'm a newbie to embedded software development.
I have a Zynq Ultrascale board that has an Axi DMA in its Hardware and I want to access this DMA from Linux.
I know I should use DMA-Engine to Access DMA in Linux and I found the following link which is the Xilinx DMA driver, but I can't add these files to my qt project without any errors and I received file(header file) not found errors.
drivers/dma/xilinx/xilinx_dma.c
I have a piece of scattered information about the DMA driver, Device tree, and DMA-Engine but I know nothing about how to utilize these to access hardware DMA.
I built a Petalinux project and add DMA-Engine and DMA Test client to its kernel.
I don't know adding DMAEngine to the Petalinux project is enough or I should have a driver as well.
I don't know adding hardware specification (by .xsa file and .bit file) to the Petalinux project is enough or I should add a device tree to my Linux for detecting DMA as well
I lookup a step-by-step tutorial on how to set up Linux and qt creator for accessing DMA,
or at least a clear roadmap to my target.
thank you in advance.
First of all, you are facing errors when adding xilinx_dma.c to the Qt project because this file is meant to be compiled as part of kernel or as a kernel module.
Adding DMA Engine to Petalinux is not enough to work with DMA from user space. DMA Engine only provides a standardized API to let different DMAs be integrated into kernel. You need to add a client driver as well. Xilinx, as far as I know, has provided a simple client driver called DMA Proxy Driver. It also includes some simple examples that show how you can access DMA from the user space. However, if your application needs high bandwidth, you probably need to consider other options.
There is also an open source client driver for Axi DMA which achieves higher bandwidths compared to Proxy DMA Driver. It's user space API also allows you to register a callback function to be called whenever a transaction is finished.
The third option is to implement the driver in the user space. This can be done by defining the DMA as a UIO device in the device tree and access its register map directly from the user space. In this case, you need to allocate some contiguous memory blocks in the kernel space to avoid complications with MMU, which cannot be dealt with from the user space.
I have been considering using Erlang for an embedded system.
The one thing I am missing in my research is the ability to do direct memory mapping.
Is this expected to be done via a NIF (Native Interface) or some other method (if so, what)?
There is no memory mapped IO interface in the Erlang VM. You would need to use NIF or alternatively you can try to make such IO subsystem available as an file descriptor. Then erlang:open_port/2 can be used to communicate with that.
What is the difference between "Inbox driver" and "Direct Memory Mapped driver"? My basic LED blink remote application worked only after selecting Direct Memory mapped driver. What is the unique things associated with this driver?
The Direct Memory Mapped Driver(DMAP) is an in-developement driver that provides GPIO performance improvements over the default inbox driver. If you use Lighting Driver in your application, you should set the controller driver as Direct Memory Mapped Driver,or there will be exception thrown.As far as i know,there is no more official statement about the detailed difference.
I heard about USB to LPT adapters that are capable of mapping PC legacy parallel port address. What is the level of such mapping? I mean - is it possible to access the adpater's pins by using 'in' or 'out' x86 assembler instructions (in Windows or Linux)? If not, what does it mean that the addresses are mapped? What kind of emulation is this?
Thanks.
Marcin
A mapping from legacy I/O port addresses to a USB device is most likely handled by trapping the port access in kernel mode operating system code. For several generations of systems now, the operating system has been able to impose itself between application code and the hardware in such a way that even things that look like raw hardware access to the application are not necessarily so.
Effectively, when the processor comes upon that raw port access, it isn't executed but an operating system service routine is called instead.