DMA

Overview

API Reference

group dma_interface

DMA Interface.

Typedefs

typedef void (*dma_callback_t)(const struct device *dev, void *user_data, uint32_t channel, int status)

Callback function for DMA transfer completion.

If enabled, callback function will be invoked at transfer completion or when error happens.

Parameters

  • dev: Pointer to the DMA device calling the callback.

  • user_data: A pointer to some user data or NULL

  • channel: The channel number

  • status: 0 on success, a negative errno otherwise

Enums

enum dma_channel_direction

Values:

enumerator MEMORY_TO_MEMORY
enumerator MEMORY_TO_PERIPHERAL
enumerator PERIPHERAL_TO_MEMORY
enumerator PERIPHERAL_TO_PERIPHERAL
enum dma_addr_adj

Valid values for source_addr_adj and dest_addr_adj

Values:

enumerator DMA_ADDR_ADJ_INCREMENT
enumerator DMA_ADDR_ADJ_DECREMENT
enumerator DMA_ADDR_ADJ_NO_CHANGE

Functions

int dma_config(const struct device *dev, uint32_t channel, struct dma_config *config)

Configure individual channel for DMA transfer.

Parameters

  • dev: Pointer to the device structure for the driver instance.

  • channel: Numeric identification of the channel to configure

  • config: Data structure containing the intended configuration for the selected channel

Return Value

  • 0: if successful.

  • Negative: errno code if failure.

int dma_reload(const struct device *dev, uint32_t channel, uint32_t src, uint32_t dst, size_t size)

Reload buffer(s) for a DMA channel.

Parameters

  • dev: Pointer to the device structure for the driver instance.

  • channel: Numeric identification of the channel to configure selected channel

  • src: source address for the DMA transfer

  • dst: destination address for the DMA transfer

  • size: size of DMA transfer

Return Value

  • 0: if successful.

  • Negative: errno code if failure.

int dma_start(const struct device *dev, uint32_t channel)

Enables DMA channel and starts the transfer, the channel must be configured beforehand.

Implementations must check the validity of the channel ID passed in and return -EINVAL if it is invalid.

Parameters

  • dev: Pointer to the device structure for the driver instance.

  • channel: Numeric identification of the channel where the transfer will be processed

Return Value

  • 0: if successful.

  • Negative: errno code if failure.

int dma_stop(const struct device *dev, uint32_t channel)

Stops the DMA transfer and disables the channel.

Implementations must check the validity of the channel ID passed in and return -EINVAL if it is invalid.

Parameters

  • dev: Pointer to the device structure for the driver instance.

  • channel: Numeric identification of the channel where the transfer was being processed

Return Value

  • 0: if successful.

  • Negative: errno code if failure.

int dma_get_status(const struct device *dev, uint32_t channel, struct dma_status *stat)

get current runtime status of DMA transfer

Implementations must check the validity of the channel ID passed in and return -EINVAL if it is invalid or -ENOSYS if not supported.

Parameters

  • dev: Pointer to the device structure for the driver instance.

  • channel: Numeric identification of the channel where the transfer was being processed

  • stat: a non-NULL dma_status object for storing DMA status

Return Value

  • non-negative: if successful.

  • Negative: errno code if failure.

uint32_t dma_width_index(uint32_t size)

Look-up generic width index to be used in registers.

WARNING: This look-up works for most controllers, but may not work for yours. Ensure your controller expects the most common register bit values before using this convenience function. If your controller does not support these values, you will have to write your own look-up inside the controller driver.

Parameters

  • size: width of bus (in bytes)

Return Value

  • common: DMA index to be placed into registers.

uint32_t dma_burst_index(uint32_t burst)

Look-up generic burst index to be used in registers.

WARNING: This look-up works for most controllers, but may not work for yours. Ensure your controller expects the most common register bit values before using this convenience function. If your controller does not support these values, you will have to write your own look-up inside the controller driver.

Parameters

  • burst: number of bytes to be sent in a single burst

Return Value

  • common: DMA index to be placed into registers.

struct dma_block_config
#include <dma.h>

DMA block configuration structure.

source_address is block starting address at source source_gather_interval is the address adjustment at gather boundary dest_address is block starting address at destination dest_scatter_interval is the address adjustment at scatter boundary dest_scatter_count is the continuous transfer count between scatter boundaries source_gather_count is the continuous transfer count between gather boundaries block_size is the number of bytes to be transferred for this block.

config is a bit field with the following parts: source_gather_en [ 0 ] - 0-disable, 1-enable dest_scatter_en [ 1 ] - 0-disable, 1-enable source_addr_adj [ 2 : 3 ] - 00-increment, 01-decrement, 10-no change dest_addr_adj [ 4 : 5 ] - 00-increment, 01-decrement, 10-no change source_reload_en [ 6 ] - reload source address at the end of block transfer 0-disable, 1-enable dest_reload_en [ 7 ] - reload destination address at the end of block transfer 0-disable, 1-enable fifo_mode_control [ 8 : 11 ] - How full of the fifo before transfer start. HW specific. flow_control_mode [ 12 ] - 0-source request served upon data availability 1-source request postponed until destination request happens reserved [ 13 : 15 ]

struct dma_config
#include <dma.h>

DMA configuration structure. 

dma_slot             [ 0 : 6 ]   - which peripheral and direction
                                   (HW specific)
channel_direction    [ 7 : 9 ]   - 000-memory to memory,
                                   001-memory to peripheral,
                                   010-peripheral to memory,
                                   011-peripheral to peripheral,
                                   ...
complete_callback_en [ 10 ]       - 0-callback invoked at completion only
                                   1-callback invoked at completion of
                                     each block
error_callback_en    [ 11 ]      - 0-error callback enabled
                                   1-error callback disabled
source_handshake     [ 12 ]      - 0-HW, 1-SW
dest_handshake       [ 13 ]      - 0-HW, 1-SW
channel_priority     [ 14 : 17 ] - DMA channel priority
source_chaining_en   [ 18 ]      - enable/disable source block chaining
                                   0-disable, 1-enable
dest_chaining_en     [ 19 ]      - enable/disable destination block
                                   chaining.
                                   0-disable, 1-enable
linked_channel       [ 20 : 26 ] - after channel count exhaust will
                                   initiate a channel service request
                                   at this channel
reserved             [ 27 : 31 ]

source_data_size    [ 0 : 15 ]   - width of source data (in bytes)
dest_data_size      [ 16 : 31 ]  - width of dest data (in bytes)
source_burst_length [ 0 : 15 ]   - number of source data units
dest_burst_length   [ 16 : 31 ]  - number of destination data units

block_count  is the number of blocks used for block chaining, this
depends on availability of the DMA controller.

user_data  private data from DMA client.

dma_callback see dma_callback_t for details

struct dma_status
#include <dma.h>

DMA runtime status structure

busy - is current DMA transfer busy or idle dir - DMA transfer direction pending_length - data length pending to be transferred in bytes or platform dependent.