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PCI Express Multi-Channel DMA Interface
2014.12.15
UG-01160
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The PCI Express® DMA Multi-Channel Controller Example Design provides multi-channel support for
the Stratix® V Avalon® Memory-Mapped (Avalon-MM) DMA for PCI Express IP Core. Up to eight
external DMA controllers drive DMA descriptors to the PCI Express Multi-Channel DMA Avalon
Streaming (Avalon-ST) sink interfaces. The PCI Express Multi-Channel DMA arbitrates between the
descriptor queues, taking into account the request priority and the weight. The Data Mover is a module in
the soft-logic bridge in the Stratix V Avalon-MM DMA for PCI Express IP Core.
Figure 1: PCI Express Multi-Channel DMA Interface Example Design System-Level Block Diagram
PCI Express
Multi-Channel
DMA Interface
Src
DMA
Controller0
Sink
Rd & Wr Descriptors0
Completion Status0
Sink
Src
Src
DMA
Controller7 Sink
Completion Status7
Control Register Access
Data Mover
Rd & Wr Sub-Descriptors
Sink
Src
Sink
Rd & Wr Descriptors7
Avalon-MM DMA for PCI Express
Completion Status
Src
Avalon Streaming
256 bits PCIe TLP
Sink
Src
PCIe
Hard IP
G3X8
Mstr
Slave
Mstr
Memory
Slave
Slave
Avalon-MM 256 bits
Avalon-MM 256 bits
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PCI Express Multi-Channel DMA Interface
Figure 2: PCI Express Multi-Channel DMA Interface Internals Block Diagram
Priority
ID
Dest
Source
Length
End
Orig. ID
Sub-ID
Dest
Source
Length
Channel 0
Fragmentation
Priority Sort
4X
Channel 1
Fragmentation
Priority Sort
4X
Priority Queue 0
Priority Queue 1
Channel 7
Status to
Controller
Completion
StatusCompletion
Counter 16x
StatusCompletion
Counter 16x
StatusCompletion
Counter 16x
Status Counters
Fragmentation
Priority Sort
4X
Scheduler
Descriptor
to Data Mover
Status from
Data Mover
Descriptor
Removal
Status Queue
Slave
Avalon-MM
Slave
Multi-Channel
Control Registers
(Abort, pause)
Original ID 0 Mapped to > 0 - 7
Original ID 1 Mapped to > 8 - 15
Original ID 2 Mapped to > 16 - 23
Original ID 3 Mapped to > 24 - 31
Original ID 4 Mapped to > 32-39
Original ID 31 Mapped to > 248 - 255
Multi-Channel Adapter
The PCI Express Multi-Channel DMA Interface Example Design performs the following functions:
•
•
•
•
•
•
Stores up to four outstanding descriptors for each channel before deasserting the ready signal
Divides each descriptor into subdescriptors with a payload size of 512 bytes
Arbitrates between two priority queues based on the Channel Priority Weight
Tracks the completion status of the 32 possible outstanding descriptors
Forwards completion status to the DMA Controllers
Removes descriptors from internal queues on successful completion and in response to a requests
received on its Avalon-MM Control register interface
• When multi-function support is enabled, maps function numbers to channel numbers.
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Device Family Support
3
Note: The PCI Express Multi-Channel DMA Interface Example Design is preliminary in the current
release. Both the programming model and top-level signals may change in subsequent releases.
Device Family Support
Table 1: Device Family Support
Device Family
Support
Stratix V
Final. The IP core is verified with final timing
models. The IP core meets all functional and timing
requirements for the device family and can be used
in production designs.
Other device families
No support.
Parameters
The PCIe® Multi-Channel DMA Interface Example Design has three parameters that you can specify to
customize its function.
Table 2: Parameteres
Parameter Name
Value
Description
Number of channels
2, 4, 8
Specifies the number of channels.
Channel priority weight
0, 4, 8
The arbiter uses the Channel priority weight in combina‐
tion with the descriptor priority bit to calculate the ratio of
transmission between priority queues.
Descriptor width
161, 169
Specifies the width of the descriptor. When you select 169,
the low-order 8 bits specify the function number for variants
with SR-IOV enabled.
PCIe Multi-Channel DMA Interfaces
The PCIe Multi-Channel DMA Interface Example Design interfaces receive DMA descriptors on up to
eight Descriptor Controller Avalon-ST RX interfaces. It drives the selected descriptor to the Data Mover
using its single Descriptor Avalon-ST TX interface. The Data Mover drives status to the PCIe MultiChannel DMA on the Descriptor Status Avalon-ST RX interface. The PCIe Multi-Channel DMA forwards
status to the DMA controllers on its Descriptor Status Avalon-ST source interfaces. An Avalon-MM slave
interface allows DMA controllers to remove descriptors from the PCIe Multi-Channel DMA internal
queues.
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PCIe Multi-Channel DMA Descriptor Interfaces
PCI Express Multi-Channel DMA Controller IP Core
Descriptor
Controller0
RX
Descriptor
Controller7
RX
DescInstr0_i[168 or 160:0]
DescInstrValid0_i
DescInstrReady0_o
DescInstr7_i[167:0]
DescInstrValid7_i
DescInstrReady7_o
Completion
Status0
DmaTxData0_o[31:0]
DmaTxValid0_o
Completion
Status7
DmaTxData7_o[31:0]
DmaTxValid7_o
Control
Register
DmaRxData_o[159:0]
DmaRxValid_o
DmaRxReady_i
Descriptor
TX
DmaTxData_i[31:0]
DmaTxValid_i
Descriptor
Status RX
MCSlaveChipSelect_i
MCSlaveWrite_i
MCSlaveAddress_i[13:0]
MCSlaveWriteData_i[31:0]
MCSlaveWaitRequect_o
clk_i
rstn_i
Related Information
Avalon Interface Specifications
PCIe Multi-Channel DMA Descriptor Interfaces
Table 3: Descriptor Controller RX Interface
This is an Avalon-ST sink interface. It is synchronous to clk_i.
Signal Name
DescInstr<n>i[168 or
160:0]
Direction
Input
Description
Write descriptor or data moving instruction. When SRIOV is enabled, the bus has the following layout:
• [168:161]: Function number
• [160]: Priority
• [159:0]: Descriptor
Otherwise, the bus has the following layout:
• [160]: Priority
• [159:0] Descriptor
This is the format that the Data Mover included in the
Avalon-MM DMA for PCI Express requires.
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Control Register Interface
Signal Name
Direction
DescInstrValid<n> _i
Input
When asserted, indicates that DescInstr<n>_i is valid.
DescInstrReady<n> _o
Output
When asserted, indicates that the channel can accept
new descriptors. The ready latency on this interface is 0
cycles. The Multi-Channel DMA Controller stores data
on the rising edge of clock whenever DescInstrReady<n> and DescInstrValid<n> are both asserted.
5
Description
Table 4: Descriptor Status Interface
This is an Avalon-ST source interface.
Signal Name
Direction
DmaTxData<n>_o[31:0]
Output
Description
Specifies the status for the descriptor ID specified. The
following fields are defined:
• [31:14]: Reserved
• [13:12]: Status code
• 2'b00: Descriptor completed successfully
• 2'b01: Descriptor removal completed successfully
• 2'b10: Descriptor partially removed
• 2'b11: Descriptor removal failed
• [11:8]: Reserved
• [7:0]: Descriptor ID whose status is being reported
DmaTxValid<n>_o
Output
When asserted, indicates that DmaTxData<n>_o[31:0]
is valid. This interface does not have a ready input. The
requesting controller must be able to store data
whenever DmaTxValid<n> is asserted.
Control Register Interface
To cancel a pending descriptor, a DMA controller writes the descriptor ID to the Avalon-MM slave
interface. The Mulit-Channel DMA Interface IP Core drives the status of this request on the Descriptor
Status interface of the requesting controller.
Table 5: Control Register Interface
This is an Avalon-MM slave interface. It is synchronous to clk_i.
Signal Name
Direction
MCSlaveChipSelect_i
Input
When asserted, the other signals in this interface are
driving valid data.
MCSlaveWrite_i
Input
Asserted to perform a write.
MCSlaveAddress_i[13:0]
Input
Specifies the address of the Control Register AvalonMM slave interface.
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Descriptor TX Interface
Signal Name
MCSlaveWriteData_
i[31:0]
Direction
Input
Description
Specifies the ID for the of the descriptor being deleted.
The status of this request is reported on the appropriate
Control Status interface.
Note: When removal of a descriptor is requested,
internal logic searches the pipeline and
buffers for the descriptor ID. It may not find
the ID requested. The requesting controller
must manage appropriately, based on the
status reported on the Control Status
interface.
MCSlaveWaitRequest_o
Input
When asserted, this interface is not ready to accept
commands.
Descriptor TX Interface
Table 6: Descriptor TX Interface to Data Mover
This is an Avalon-ST source interface. It is synchronous to clk_i.
Signal Name
Direction
Description
Output
The DMA Multi-Channel Controller drives descriptor
data to the Data Mover on this Avalon-ST source
interface. (It uses priority bit[160] internally and does
not drive it to the Data Mover.
DmaRxValid_o
Output
When asserted, the data on DmaRxData_o is valid.
DmaRxReady_i
Input
DmaRxData_o[167 or
159:0]
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When asserted, the Data Mover is ready to accept new
descriptors. The ready latency on this interface is 3
cycles. Consequently, the DMA Multi-Channel
Controller must stop driving valid data within 3 cycles
of the deassertion of DmaRxReady_i.
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Table 7: Descriptor Status Interface
This is an Avalon-ST sink interface. the
Signal Name
DmaTxData_i[31:0]
Direction
Input
Description
The Data Mover drives status to the DMA MultiChannel Controller on this Avalon-ST interface.
Specifies the status for the descriptor ID specified. The
following fields are defined:
• [31:14]: Reserved. All 0s.
• [13:12]: Status cod.e
• 2'b00: Descriptor completed successfully.
• 2'b01: Descriptor removal completed successfully.
• 2'b10: Descriptor partially removed. Part of the
descriptor has already been processed. The
controller must include logic to process partial
completion data.
• 2'b11: Descriptor removal failed.
• [11:8]: Reserved. All 0s.
• [7:0]: Descriptor ID whose status is being reported.
DmaTxValid_i_i
Input
When asserted, indicates that DmaTxData_i[31:0] is
valid.
Example Design
You can download a Qsys example design that illustrates the use of this component from the install
directory, <install_dir>ip/altera/altera_pcie/altera_pcie_hip_256_avmm/channelizer/example_design/.
This example design includes the following Qsys files:
• mc_top_g3x8_4ch.qsys—This is the top-level Qsys file that connects the DUT and APPS components.
• sriov_mcdma_app_g3x8_256b.qsys—This Qsys system connects an example Avalon-MM DMA for PCI
Express with Single Root I/O Virtualization (SR-IOV) to read and write descriptor controllers and
SRAM.
• rddc_mc_256b.qsys—This Qsys system connects four read descriptor controllers the the PCI Express
DMA Multi-Channnel Controller IP Core.
• wrdc_mc_256b.qsys—This Qsys system connects four write descriptor controllers the the PCI Express
DMA Multi-Channnel Controller IP Core.
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Revision History
Figure 3: Qsys Sub-System with Four Write Descriptor Controllers and the DMA Multi-Channnel
Controller
Revision History
Date
2014.12.15
Altera Corporation
Version
14.1
Changes
• Initial Release.
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