Building and Installing Software Stack¶

For building the Linux QDMA Driver, make sure the System Requirements are satisfied.

Updating the PCIe device ID¶

During the PCIe DMA IP customization in Vivado you can specify a PCIe Device ID. This Device ID must be recognized by the driver in order to properly identify the PCIe QDMA device. The current driver is designed to recognize the default PCIe Device IDs that get generated with the PCIe example design. If the PCIe Device ID is modified during IP customization, one needs to modify QDMA driver to recognize this new ID.

User can also remove PCIe Device IDs that are not be used in their solution.

To modify the PCIe Device ID in the driver, open the driver/src/pci_ids.h file from the driver source and search for the pci_device_id struct. This struct defines the PCIe Device IDs that are recognized by the driver in the following format:

{PCI_DEVICE (0x10ee, 0x9034),},

Add, remove, or modify the PCIe Device IDs in this struct. The PCIe DMA driver will only recognize device IDs identified in this struct as PCIe QDMA devices. Once modified, the driver must be un-installed and recompiled.

Building the QDMA Driver Software¶

This driver software supports both Physical Functions (PF) and Virtual Functions (VF).

In order to compile the Xilinx QDMA software, configured and compiled Linux kernel source tree is required. Linux QDMA driver is dependent on libaio. Hence, make sure to install libaio before compiling the QDMA driver. Example command is provided on Ubuntu. Follow the similar procedure for other OS flavors.

[xilinx@]# sudo apt-get install libaio libaio-devel

The source tree may contain only header files, or a complete tree. The source tree needs to be configured and the header files need to be compiled. The Linux kernel must be configured to use modules.

Linux QDMA Driver software can be found on the Xilinx github https://github.com/Xilinx/dma_ip_drivers/tree/master/QDMA/linux-kernel Below is the directory structure of the Linux QDMA Driver software.

Directory	Description
apps/	User space application to configure and control QDMA
docs/	Documentation for the Xilinx QDMA Linux Driver
driver/src	Provides interfaces to manage the PCIe device and exposes character driver interface to perform QDMA transfers
driver/libqdma/	QDMA library to configure and control the QDMA IP
scripts/	Sample scripts for perform DMA operations
Makefile	Makefile to compile the driver
RELEASE.txt	Release Notes

Once driver sources are downloaded, compile the QDMA Driver software

[xilinx@]# make clean && make

Upon executing make, A sub-directory bin is created with the list of executable listed in below tables. Individual executables can also be built with commands listed against each component in below tables.

Optionally to enable debug mode for more detailed logs, build with the following command

[xilinx@]# make clean & make DEBUG=1

Kernel modules:

Executable	Description	Command
qdma-pf.ko	PF Driver	make driver MODULE=mod_pf
qdma-vf.ko	VF Driver	make driver MODULE=mod_vf

Applications:

Run make apps to compile all the below applications. Applications can be compiled individually as mentioned after entering the respective application directory.

Executable	Description	Command
dma-ctl	QDMA control and configuration application	make dma-ctl
dma-to-device	Performs a host-to-card transaction for MM or ST	make dma-to-device
dma-from-device	Performs a card-to-host transaction for MM or ST	make dma-from-device
dma-perf	Measures the performance of QDMA IP	make dma-perf
dma-latency	Measures the ping pong latency for ST transfers	make dma-latency
dma-xfer	Sample transfer application	make dma-xfer

Install the executable by running “make install”

PF/VF kernel modules and application binaries are generated in bin and can be individually loaded
make install-apps installs the applications in /user/local/sbin.
make install-mods copies the qdma-pf.ko and qdma-vf.ko in /lib/modules/<kernel version>/qdma/

Ex: /lib/modules/4.15.0-51-generic/qdma/

Loading the QDMA Driver Module¶

Before loading the QDMA driver, make sure that the target board is connected to the Host System and required bit stream is loaded on to the board.

Make sure to install the qdma-pf.ko and qdma-vf.ko modules using the make install-mods command.

For loading the driver, execute the following command:

PF Driver:

modprobe qdma-pf

VF Driver:

modprobe qdma-vf

QDMA driver supports the following list of module parameters that can be specified while loading the driver into the Linux kernel. - Mode - Master PF - Dynamic config BAR

In order to pass the module parameters while loading a driver, a config file qdma.conf needs to be placed in /etc/modprobe.d directory. The format of the conf file would be :

options <module_name> mode=<bus_num>:<pf_num>:<mode>,<bus_num>:<pf_num>:<mode>,<bus_num>:<pf_num>:<mode>,.....
options <module_name> config_bar=<bus_num>:<pf_num>:<config_bar>,<bus_num>:<pf_num>:<config_bar>,<bus_num>:<pf_num>:<config_bar>,.....
options <module_name> master_pf=<bus_num>:<master_pf>,<bus_num>:<master_pf>

module_name: Name of the mode. For PF: qdma-pf and for VF: qdma-vf
bus_num : Bus number of the PCIe endpoint card
func_num : Function number of the corressponding bus_num
mode: Mode in which the driver needs to be loaded
config_bar: Config bar number
master_pf: Master PF
num_threads: number of threads for monitoring the writeback of completions

1. Mode¶

mode module parameter is used to specify how the completions must be processed. Each PF can be configured to function in following different modes

Auto Mode

Driver polls on the status descriptor write back updates for MM and ST H2C Mode and uses Interrupt Aggregation to process the ST C2H completions.
Poll Mode

Driver polls on the status descriptor write back updates for all modes.
Direct Interrupt Mode

A single vector is assigned to each queue and status descriptor write back updates are intimated to SW driver using interrupts.
Interrupt Aggregation Mode or Indirect Interrupt Mode

Each function creates an Interrupt Aggregation ring and status descriptor write back updates of all the queues of the function are intimated to SW driver using interrupts into this ring.
Legacy Interrupt Mode

Driver processes the status descriptor write back using legacy interrupts

By default, the mode is set to auto mode for both of the PF and VF drivers. To set other modes, the mode entry needs to be added in the qdma.conf file in the following format.

options qdma-pf mode=<bus_num>:<pf_num>:<mode>,<bus_num>:<pf_num>:<mode>,<bus_num>:<pf_num>:<mode>,.....
options qdma-vf mode=<bus_num>:<pf_num>:<mode>,<bus_num>:<pf_num>:<mode>,<bus_num>:<pf_num>:<mode>,.....

For example, if modprobe command is executed with the following config file:

options qdma-pf mode=0x06:0:2,0x06:1:3,0x06:2:0,0x07:2:1
options qdma-vf mode=0x06:0:2,0x06:1:3

PF0 of bus number 6 is loaded in Direct Interrupt mode (2)
PF1 of bus number 6 is loaded in Indirect Interrupt mode (3)
PF2 of bus number 6 is loaded in Auto mode (0)
PF2 of bus number 7 is loaded in Poll mode (1)
PF0’s VF group of bus number 6 is loaded in Direct Interrupt Mode (2)
PF1’s VF group of bus number 6 is loaded in Indirect Interrupt Mode (3)
Rest all, which are not specified, are loaded in Auto mode by default.

2. Master PF¶

master_pf module parameter is used to set the master PF for QDMA driver By default, master_pf is set to PF0(First device in the PF list)

To set other PF as a master_pf, its entry needs to be added in the qdma.conf file in the following format.

options qdma-pf master_pf=<bus_num>:<master_pf>,<bus_num>:<master_pf>

For example, if modprobe command is executed with the following config file:

options qdma-pf master_pf=0x06:0,0x07:1

Master PF of bus number 6 is set as PF0
Master PF of bus number 7 is set as PF1

3. Dynamic Config Bar¶

config_bar module parameter is used to set the DMA bar of the QDMA device. QDMA IP supports changing the DMA bar while creating the bit stream.

For 64-bit bars, DMA bar can be 0|2|4 . By default, the QDMA driver sets BAR0 as the DMA BAR

To set other config bar, the config_bar entry needs to be added in the qdma.conf file in the following format.

options qdma-pf config_bar=<bus_num>:<pf_num>:<config_bar>,<bus_num>:<pf_num>:<config_bar>,<bus_num>:<pf_num>:<config_bar>,.....
options qdma-vf config_bar=<bus_num>:<pf_num>:<config_bar>,<bus_num>:<pf_num>:<config_bar>,<bus_num>:<pf_num>:<config_bar>,.....

For example, if modprobe command is executed with the following config file:

options qdma-pf config_bar=0x06:0:0,0x06:1:2,0x06:2:4,0x07:2:0
options qdma-vf config_bar=0x06:0:2,0x06:1:0

PF0 of bus number 6 is loaded with config bar set as 0
PF1 of bus number 6 is loaded with config bar set as 2
PF2 of bus number 6 is loaded with config bar set as 4
PF2 of bus number 7 is loaded with config bar set as 0
PF0’s VF group of bus number 6 is loaded with config bar set as 2
PF1’s VF group of bus number 6 is loaded with config bar set as 0
Rest all, which are not specified, are loaded with config bar set as 0

From the examples above, a qdma.conf file would look like:

options qdma-pf mode=0x06:0:2,0x06:1:3,0x06:2:0,0x07:2:1
options qdma-pf master_pf=0x06:0,0x07:1
options qdma-pf config_bar=0x06:0:0,0x06:1:2,0x06:2:4,0x07:2:0
options qdma-vf mode=0x06:0:2,0x06:1:3
options qdma-vf config_bar=0x06:0:2,0x06:1:0

An auxillary script, qdma_generate_conf_file.sh has been added to the scripts folder which helps create the qdma.conf config file and copies it to the /etc/modprobe.d location. The script can be used as shown below -

./scripts/qdma_generate_conf_file.sh <bus_num> <num_pfs> <mode> <config_bar> <master_pf>

Please note that having the qdma-pf.ko and qdma-vf.ko files in the /lib/modules/<kernel version>/qdma/ will cause automatic loading of the driver modules at boot time. To avoid this, it is recommended to have the drivers blacklisted. This can be done by adding the below 2 lines in the /etc/modprobe.d/blacklist.conf file -

blacklist qdma-pf
blacklist qdma-vf