gd,gd32-dma-v1

Vendor: GigaDevice Semiconductor

Description

These nodes are “dma” bus nodes.

GD32 DMA controller with FIFO

channel: Select channel for data transmitting

slot: Select peripheral to connect DMA

config: A 32bit mask specifying the DMA channel configuration
  - bit 6-7:   Direction  (see dma.h)
               - 0x0: MEMORY to MEMORY
               - 0x1: MEMORY to PERIPH
               - 0x2: PERIPH to MEMORY
               - 0x3: reserved for PERIPH to PERIPH

  - bit 9:     Peripheral address increase
               - 0x0: no address increment between transfers
               - 0x1: increment address between transfers

  - bit 10:    Memory address increase
               - 0x0: no address increase between transfers
               - 0x1: increase address between transfers

  - bit 11-12: Peripheral data width
               - 0x0: 8 bits
               - 0x1: 16 bits
               - 0x2: 32 bits
               - 0x3: reserved

  - bit 13-14: Memory data width
               - 0x0: 8 bits
               - 0x1: 16 bits
               - 0x2: 32 bits
               - 0x3: reserved

  - bit 15:    Peripheral Increment Offset Size
               - 0x0: offset size is linked to the peripheral bus width
               - 0x1: offset size is fixed to 4 (32-bit alignment)

  - bit 16-17: Priority
               - 0x0: low
               - 0x1: medium
               - 0x2: high
               - 0x3: very high

fifo-threshold: A 32bit bitfield value specifying FIFO threshold
  - bit 0-1:   Depth of DMA's FIFO used by burst-transfer.
               - 0x0: 1 word
               - 0x1: 2 word
               - 0x2: 3 word
               - 0x3: 4 word


Example of devicetree configuration

&spi0 {
      status = "okay";
      pinctrl-0 = <&spi0_default>;
      pinctrl-names = "default";
      cs-gpios = <&gpioa 4 GPIO_ACTIVE_LOW>;

      dmas = <&dma1 0 3 0 0>, <&dma1 5 3 GD32_DMA_PRIORITY_HIGH 0>
      dma-names = "rx", "tx";
};

"spi0" uses dma1 for transmitting and receiving in the example.
Each is named "rx" and "tx".
The first cell assigns channel 0 to receive and channel 5 to transmit.
The second cell is slot. Both channels select 3.
What the slot number '3' means depends on the DMA controller and channel.
See the Hardware manual.
The config that places on the third can take various configs.
But the setting used depends on each driver implementation.
Set the priority for the transmitting channel as HIGH, LOW(the default) for receive channel.
The fifo-threshold cell that places the fourth is configuring FIFO threshold.
The behavior of burst transfer determines by data-width in the config cell,
burst-length in the dma_config struct, and fifo-threshold.
A single burst transfer transfers [(4 * fifo-threshold)] bytes using with DMA's FIFO.
Where (data-width * burst-length) must be multiple numbers of burst transfer size.
For example, In the case of data-width is 'byte' and burst-length is 8.
If the fifo-threshold is a 2-word case, it runs one burst transfer to transfer 8 bytes.
Or the fifo-threshold is a 4-word case, runs two times burst transfer to transferring 8 bytes each
time.

Properties

Node specific propertiesDeprecated node specific propertiesBase properties

Properties not inherited from the base binding file.

Name	Type	Details
#dma-cells	int	Number of items to expect in a DMA specifier This property is required. Constant value: 4
resets	phandle-array	Reset information
reset-names	string-array	Name of each reset
dma-channels	int	Number of DMA channels supported by the controller This property is required.
gd,mem2mem	boolean	The DMA controller supporting memory to memory transfer
dma-channel-mask	int	Bitmask of available DMA channels in ascending order that are not reserved by firmware and are available to the kernel. i.e. first channel corresponds to LSB.
dma-requests	int	Number of DMA request signals supported by the controller.
dma-buf-addr-alignment	int	Memory address alignment requirement for DMA buffers used by the controller.
dma-buf-size-alignment	int	Memory size alignment requirement for DMA buffers used by the controller.
dma-copy-alignment	int	Minimal chunk of data possible to be copied by the controller.

Specifier cell names

• dma cells: channel, slot, config, fifo-threshold