ZYNQMP and Versal DMA Linux Driver for Zynq Ultrascale+ MPSoC

Introduction

HW IP features

• AXI 4 support , burst length is limited to 16 to provide AXI 3 compatibility
• SRC and DST payload can start and end at any alignment
• Over fetching can be enabled/disabled per channel
• Up to 8 configurable DMA channels
• Each channel can be programmed secure or non-secure
• Programmable number of outstanding transactions per channel
• Support for periodic transaction scheduling. Period can be independently programmed per channel
• Supports Simple(descriptor less) and Scatter Gather (SG) DMA modes
• Supports read only DMA mode
• Supports write only DMA mode
• Common Buffer is automatically shared among all enabled DMA channels
• Support for DMA START, STOP and PAUSE
• Interrupt Accounting support
• Descriptor prefetch support to maximize DMA efficiency
• Support for error recovery
• INCR & FIXED type burst supported
• Independent AXI burst length is supported on SRC & DST Side
• Support for per channel flow control interface

Features supported in driver

• Memory to Memroy transfers are support
• Scatter Gather (SG) DMA mode is supported with assumption of contiguous memory; this is because DMA_SG support in linux framework was removed in mainline kernel as there are no consumers.
• Optional descriptor's coherence.
• Optional AXI burst length is supported for both DST and SRC side. Supported values are only power of 2 i.e 1,2,4,8 and 16
• Support 8 DMA Channels
• Interrupt Accounting Support.

Missing Features and known Issues/Limitations in Driver

• No support for flow control mode.
• No support for linear and hybrid descriptor modes
• No Support for Simple DMA mode

Kernel Configuration

config XILINX_ZYNQMP_DMA
        tristate "Xilinx ZynqMP DMA Engine"
        select DMA_ENGINE
        help
          Enable support for Xilinx ZynqMP DMA controller.

config DMATEST
        tristate "DMA Test client"
        help
          Simple DMA test client. Say N unless you're debugging a
          DMA Device driver.

config DMA_ENGINE_RAID

Devicetree

                fpd_dma_chan1: dma@fd500000 {
                        compatible = "xlnx,zynqmp-dma-1.0";
                        reg = <0x0 0xfd500000 0x0 0x1000>;
                        interrupt-parent = <&gic>;
                        interrupts = <0 124 4>;
                        clock-names = "clk_main", "clk_apb";
                        xlnx,id = <0>;
                        xlnx,bus-width = <128>;
                        power-domains = <&pd_gdma>;
                };
 
                lpd_dma_chan1: dma@ffa80000 {
                        compatible = "xlnx,zynqmp-dma-1.0";
                        reg = <0x0 0xffa80000 0x0 0x1000>;
                        interrupt-parent = <&gic>;
                        interrupts = <0 77 4>;
                        clock-names = "clk_main", "clk_apb";
                        xlnx,id = <0>;
                        xlnx,bus-width = <64>;
                        power-domains = <&pd_adma>;
                };

Test Procedure

Mainline status

Change Log

2023.2

None

2023.1

• Add device_synchronize support to allow proper termination of transfers
• Mainline updates including descriptor callback changes
• Minor coverity fixes

https://github.com/Xilinx/linux-xlnx/commits/xilinx-v2023.1/drivers/dma/xilinx/zynqmp_dma.c

2022.2

No changes

2022.1

No changes; rebased on 5.15 kernel

https://github.com/Xilinx/linux-xlnx/commits/xilinx-v2022.1/drivers/dma/xilinx/zynqmp_dma.c

2021.2

No changes

2021.1

Summary

• Minor warning fixes.

Commits:

2020.2

No changes

2020.1

Summary

Minor bugfixes including:

• Fix descriptor list handling during reset.
• Phase dma_zalloc_coherent.

Commits:

https://github.com/Xilinx/linux-xlnx/commits/xilinx-v2020.1/drivers/dma/xilinx/zynqmp_dma.c

2019.2

None

2019.1

None

(Upgraded to mainline 4.19)

2018.3

• Fixed race condition in the probe, in case of interrupt property is not present, driver is trying to free an invalid free.

• Fixed issue driver does not work when CONFIG_PM is not set and ignore_unused is not passed.
• Fixed race conditions in the prep_sg

• Fixed issues with overflow interrupt
• Added runtime PM support in the driver
• Fixed kernel doc warnings in the driver
• Fixed sparce warnings in the driver

• Added missing clock nodes for LPDDMA in zynqmp-clk.dtsi and zynqmp.dtsi files
• Updated the description for LPDDMA Channel usage in the zynqmp.dtsi

• Driver got mainlined in the 4.8 kernel version
• Existing driver in the xilinx linux distribution is in sync with the mainline driver
• Added support for Scatter/Gather feature support in the generic DMA test client driver
• Deleted the zynqmp_dmatest client driver as it is similar to the generic test client driver after adding support for the SG.

Related Links

• Linux Drivers