Last edited 10 months ago

STM32MP1 DMA

Applicable for STM32MP13x lines, STM32MP15x lines


1. Article purpose[edit source]

This article explains the STM32MP1 series DMA topology and the associated configurations recommended by ST.

2. DMA specificities per STM32 MPU devices[edit source]

2.1. STM32MP13x lines More info.png[edit source]

The STM32MP13xx MPUs feature four DMA instances:

  • 1 MDMA internal peripheral dedicated to the transfers between some internal peripherals and the external memories (DDR), and between the internal and external memories.
  • 3 DMA internal peripheral (DMA1/DMA2/DMA3) dedicated to the transfers between internal peripherals and the internal SRAM. The DMA1 and DMA2 instances are coupled with DMAMUX1. DMA3 is coupled with DMAMUX2: DMAMUX internal peripheral is in charge of routing the internal peripheral requests to the DMA channels.
Info white.png Information
Transfers between internal peripherals and DDR, via DMA1/DMA2/DMA3, are possible but not recommended for high-bandwidth or latency-critical transfers.

2.2. STM32MP15x lines More info.png[edit source]

The STM32MP15xx MPUs feature three DMA instances:

  • 1 MDMA internal peripheral dedicated to the transfers between some internal peripherals and the external memories (DDR), and between the internal and external memories.
  • 2 DMA internal peripheral (DMA1/DMA2) dedicated to the transfers between internal peripherals and the internal SRAM. These two DMA instances are coupled with a DMAMUX internal peripheral in charge of routing the internal peripheral requests to the DMA channels.
Info white.png Information
Transfers between internal peripherals and DDR, via DMA1/DMA2, are possible but not recommended for high-bandwidth or latency-critical transfers.

3. DMA configurations[edit source]

The following figures show the different DMA configurations available on STM32MP1 and the associated requests and data connections. The legend below illustrates the request lines and datapath.

DMA legend.png
  • Internal peripherals - internal SRAM with DMA transfer
DMA transfer.png
In this configuration, the dataflow is:
  • peripheral to memory direction: data are directly transferred from the peripheral to the final internal RAM buffer by DMA.
  • memory to peripheral direction: data are transferred from the original internal SRAM buffer to the peripheral by DMA.
  • Internal peripherals - DDR with MDMA transfer
MDMA transfer.png
In this configuration, the dataflow is:
  • peripheral to memory direction: data are directly transferred from the peripheral to the final DDR buffer by MDMA.
  • memory to peripheral direction: data are transferred from the original DDR buffer to the peripheral by MDMA.
  • Internal peripherals - DDR with DMA - MDMA chained transfer
DMA MDMA transfer.png
In this configuration, the dataflow is:
  • peripheral to memory direction: data are transferred from the peripheral to the temporary internal SRAM buffer by DMA, then from the temporary internal SRAM buffer to the DDR buffer by MDMA.
  • memory to peripheral direction: data are transferred from the DDR buffer to the temporary internal SRAM buffer by MDMA, then from the temporary internal SRAM buffer to the peripheral by DMA.

For more information about the DMA controllers above, and to know the DMA configuration that must be used with each internal peripheral, refer to reference manuals corresponding to the used STM32 MPU .

4. STMicroelectronics recommendations[edit source]

4.1. For Arm® Cortex®-M4 execution context[edit source]

The Arm® Cortex®-M4 accesses by default the internal SRAM for code and data.
In this context, the DMA transfers operate only between the peripheral and the internal SRAM.
This is why ST recommends to dedicate one DMA internal peripheral to Arm® Cortex®-M4.

4.2. For Arm® Cortex®-A7 secure execution context[edit source]

The Arm® Cortex®-A7 secure firmware is located in SYSRAM (both code and data). As the internal peripherals and the SYSRAM associated to the Arm® Cortex®-A7 secure context are also secure, the MDMA must be used to support transfers between them because it is secure aware.

4.3. Arm® Cortex®-A7 nonsecure execution context[edit source]

The Arm® Cortex®-A7 nonsecure firmware is mainly located in the external memory (DDR). In consequence, the DMA transfers operate between the peripherals and the DDR. Nevertheless, as the different internal peripherals do not have the same requirements in term of bandwidth, real time, and flow control, the user must use one of the three DMA configurations described in DMA configurations. To make the selection easier, the following table sums up the possible choices for each peripheral and highlights the recommended configuration. Note that this configuration is set by default in the device tree (dtsi).

Peripheral no DMA mode DMA mode MDMA mode DMA-MDMA chaining mode Default mode
U(S)ART Yes Yes Except instance 1 Yes Only instance 1 Yes no DMA mode
ADC Yes Yes No Yes DMA-MDMA chaining mode
SPI Yes Yes Yes Only instance 6 No DMA or MDMA mode depending on instance
SPDIFRx No Yes No No DMA mode
SAI No Yes No No DMA mode
I2C Yes Yes Yes Only instances 4 and 6 No DMA or MDMA mode depending on instance
Timer Yes Yes No Yes DMA-MDMA chaining mode
DFSDM Yes Yes No No DMA mode
I2S No Yes No No DMA mode
DCMI No No No Yes DMA-MDMA chaining mode
FMC No No Yes No MDMA mode
QUADSPI No No Yes No MDMA mode
HASH No No Yes No MDMA mode
CRYP No No Yes No MDMA mode

5. STMicroelectronics reference boards default configuration[edit source]

5.1. STM32MP135x-DK Discovery kit More info green.png DMA configuration[edit source]

The following table provides the list of the peripherals for which DMA is configured. Associated configurations are also described.

Peripheral Request line DMA mode
ADC1 rx DMA-MDMA chaining mode
ADC2 rx DMA-MDMA chaining mode
CRYP1 in MDMA mode
out
HASH1 in MDMA mode
I2S2 rx DMA mode
tx
SAI2 a - tx DMA mode
b - rx
USART2 rx DMA mode
tx

5.2. STM32MP157x-EV1 Evaluation board More info green.png DMA configuration[edit source]

The following table provides the list of the peripherals for which DMA is configured. Associated configurations are also described.

Peripheral Request line DMA mode
CRYP1 in MDMA mode
out
DCMI tx DMA-MDMA chaining mode
DFSDM channel 0 - rx DMA mode
channel 1 - rx
channel 2 - rx
channel 3 - rx
HASH1 in MDMA mode
I2S2 rx DMA mode
tx
SAI2 a - tx DMA mode
b - rx
USART2 rx DMA mode
tx

5.3. STM32MP157x-DK2 Discovery kit More info green.png DMA configuration[edit source]

The following table provides the list of the peripherals for which DMA is configured. Associated configurations are also described.

Peripheral Request line DMA mode
CRYP1 in MDMA mode
out
HASH1 in MDMA mode
I2S2 rx DMA mode
tx
SAI2 a - tx DMA mode
b - rx
USART2 rx DMA mode
tx