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SAM Direct Memory Access Controller (DMAC) Driver

This driver for Atmel® | SMART ARMĀ®-based microcontrollers provides an interface for the configuration and management of the Direct Memory Access Controller(DMAC) module within the device.

The DMAC can transfer data between memories and peripherals, and thus off-load these tasks from the CPU. The module supports peripheral to peripheral, peripheral to memory, memory to peripheral, and memory to memory transfers.

The following peripheral is used by the DMAC Driver:

The following devices can use this module:

The outline of this documentation is as follows:

Prerequisites

There are no prerequisites for this module.

Module Overview

SAM devices with DMAC enables high data transfer rates with minimum CPU intervention and frees up CPU time. With access to all peripherals, the DMAC can handle automatic transfer of data to/from modules. It supports static and incremental addressing for both source and destination.

The DMAC when used with Event System or peripheral triggers, provides a considerable advantage by reducing the power consumption and performing data transfer in the background. For example, if the ADC is configured to generate an event, it can trigger the DMAC to transfer the data into another peripheral or SRAM. The CPU can remain in sleep during this time to reduce the power consumption.

Device Dma channel number
SAM D21/R21/C20/C21 12
SAM D09/D10/D11 6
SAM L21,SAMR30/R34/R35 16
SAM R34/R35 12

The DMA channel operation can be suspended at any time by software, by events from event system, or after selectable descriptor execution. The operation can be resumed by software or by events from the event system. The DMAC driver for SAM supports four types of transfers such as peripheral to peripheral, peripheral to memory, memory to peripheral, and memory to memory.

The basic transfer unit is a beat, which is defined as a single bus access. There can be multiple beats in a single block transfer and multiple block transfers in a DMA transaction. DMA transfer is based on descriptors, which holds transfer properties such as the source and destination addresses, transfer counter, and other additional transfer control information. The descriptors can be static or linked. When static, a single block transfer is performed. When linked, a number of transfer descriptors can be used to enable multiple block transfers within a single DMA transaction.

The implementation of the DMA driver is based on the idea that the DMA channel is a finite resource of entities with the same abilities. A DMA channel resource is able to move a defined set of data from a source address to destination address triggered by a transfer trigger. On the SAM devices there are 12 DMA resources available for allocation. Each of these DMA resources can trigger interrupt callback routines and peripheral events. The other main features are:

A simplified block diagram of the DMA Resource can be seen in the figure below.

Driver Feature Macro Definition

Driver Feature Macro Supported devices
FEATURE_DMA_CHANNEL_STANDBY SAM L21/L22/C20/C21/R30/R34/R35
Note
The specific features are only available in the driver when the selected device supports those features.

Terminology Used in DMAC Transfers

Name Description
Beat It is a single bus access by the DMAC. Configurable as 8-bit, 16-bit, or 32-bit.
Burst It is a transfer of n-beats (n=1,4,8,16). For the DMAC module in SAM, the burst size is one beat. Arbitration takes place each time a burst transfer is completed.
Block transfer A single block transfer is a configurable number of (1 to 64k) beat transfers

DMA Channels

The DMAC in each device consists of several DMA channels, which along with the transfer descriptors defines the data transfer properties.

With a successful DMA resource allocation, a dedicated DMA channel will be assigned. The channel will be occupied until the DMA resource is freed. A DMA resource handle is used to identify the specific DMA resource. When there are multiple channels with active requests, the arbiter prioritizes the channels requesting access to the bus.

DMA Triggers

DMA transfer can be started only when a DMA transfer request is acknowledged/granted by the arbiter. A transfer request can be triggered from software, peripheral, or an event. There are dedicated source trigger selections for each DMA channel usage.

DMA Transfer Descriptor

The transfer descriptor resides in the SRAM and defines these channel properties.

Field name Field width
Descriptor Next Address 32 bits
Destination Address 32 bits
Source Address 32 bits
Block Transfer Counter 16 bits
Block Transfer Control 16 bits

Before starting a transfer, at least one descriptor should be configured. After a successful allocation of a DMA channel, the transfer descriptor can be added with a call to dma_add_descriptor(). If there is a transfer descriptor already allocated to the DMA resource, the descriptor will be linked to the next descriptor address.

DMA Interrupts/Events

Both an interrupt callback and an peripheral event can be triggered by the DMA transfer. Three types of callbacks are supported by the DMA driver: transfer complete, channel suspend, and transfer error. Each of these callback types can be registered and enabled for each channel independently through the DMA driver API.

The DMAC module can also generate events on transfer complete. Event generation is enabled through the DMA channel, event channel configuration, and event user multiplexing is done through the events driver.

The DMAC can generate events in the below cases:

Special Considerations

There are no special considerations for this module.

Extra Information

For extra information, see Extra Information for DMAC Driver. This includes:

Examples

For a list of examples related to this driver, see Examples for DMAC Driver.

API Overview

Data Structures

struct  dma_descriptor_config
 DMA transfer descriptor configuration. More...
 
struct  dma_events_config
 Configurations for DMA events. More...
 
struct  dma_resource
 Structure for DMA transfer resource. More...
 
struct  dma_resource_config
 DMA configurations for transfer. More...
 

Macros

#define DMA_INVALID_CHANNEL   0xff
 DMA invalid channel number. More...
 

Typedefs

typedef void(* dma_callback_t )(struct dma_resource *const resource)
 Type definition for a DMA resource callback function. More...
 

Enumerations

enum  dma_address_increment_stepsize {
  DMA_ADDRESS_INCREMENT_STEP_SIZE_1 = 0,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_2,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_4,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_8,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_16,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_32,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_64,
  DMA_ADDRESS_INCREMENT_STEP_SIZE_128
}
 Address increment step size. More...
 
enum  dma_beat_size {
  DMA_BEAT_SIZE_BYTE = 0,
  DMA_BEAT_SIZE_HWORD,
  DMA_BEAT_SIZE_WORD
}
 The basic transfer unit in DMAC is a beat, which is defined as a single bus access. More...
 
enum  dma_block_action {
  DMA_BLOCK_ACTION_NOACT = 0,
  DMA_BLOCK_ACTION_INT,
  DMA_BLOCK_ACTION_SUSPEND,
  DMA_BLOCK_ACTION_BOTH
}
 Block action definitions. More...
 
enum  dma_callback_type {
  DMA_CALLBACK_TRANSFER_ERROR,
  DMA_CALLBACK_TRANSFER_DONE,
  DMA_CALLBACK_CHANNEL_SUSPEND,
  DMA_CALLBACK_N
}
 Callback types for DMA callback driver. More...
 
enum  dma_event_input_action {
  DMA_EVENT_INPUT_NOACT,
  DMA_EVENT_INPUT_TRIG,
  DMA_EVENT_INPUT_CTRIG,
  DMA_EVENT_INPUT_CBLOCK,
  DMA_EVENT_INPUT_SUSPEND,
  DMA_EVENT_INPUT_RESUME,
  DMA_EVENT_INPUT_SSKIP
}
 DMA input actions. More...
 
enum  dma_event_output_selection {
  DMA_EVENT_OUTPUT_DISABLE = 0,
  DMA_EVENT_OUTPUT_BLOCK,
  DMA_EVENT_OUTPUT_RESERVED,
  DMA_EVENT_OUTPUT_BEAT
}
 Event output selection. More...
 
enum  dma_priority_level {
  DMA_PRIORITY_LEVEL_0,
  DMA_PRIORITY_LEVEL_1,
  DMA_PRIORITY_LEVEL_2,
  DMA_PRIORITY_LEVEL_3
}
 DMA priority level. More...
 
enum  dma_step_selection {
  DMA_STEPSEL_DST = 0,
  DMA_STEPSEL_SRC
}
 DMA step selection. More...
 
enum  dma_transfer_trigger_action {
  DMA_TRIGGER_ACTION_BLOCK = DMAC_CHCTRLB_TRIGACT_BLOCK_Val,
  DMA_TRIGGER_ACTION_BEAT = DMAC_CHCTRLB_TRIGACT_BEAT_Val,
  DMA_TRIGGER_ACTION_TRANSACTION = DMAC_CHCTRLB_TRIGACT_TRANSACTION_Val
}
 DMA trigger action type. More...
 

Functions

void dma_abort_job (struct dma_resource *resource)
 Abort a DMA transfer. More...
 
enum status_code dma_add_descriptor (struct dma_resource *resource, DmacDescriptor *descriptor)
 Add a DMA transfer descriptor to a DMA resource. More...
 
enum status_code dma_allocate (struct dma_resource *resource, struct dma_resource_config *config)
 Allocate a DMA with configurations. More...
 
void dma_descriptor_create (DmacDescriptor *descriptor, struct dma_descriptor_config *config)
 Create a DMA transfer descriptor with configurations. More...
 
static void dma_descriptor_get_config_defaults (struct dma_descriptor_config *config)
 Initializes DMA transfer configuration with predefined default values. More...
 
static void dma_disable_callback (struct dma_resource *resource, enum dma_callback_type type)
 Disable a callback function for a dedicated DMA resource. More...
 
static void dma_enable_callback (struct dma_resource *resource, enum dma_callback_type type)
 Enable a callback function for a dedicated DMA resource. More...
 
enum status_code dma_free (struct dma_resource *resource)
 Free an allocated DMA resource. More...
 
void dma_get_config_defaults (struct dma_resource_config *config)
 Initializes config with predefined default values. More...
 
static enum status_code dma_get_job_status (struct dma_resource *resource)
 Get DMA resource status. More...
 
static bool dma_is_busy (struct dma_resource *resource)
 Check if the given DMA resource is busy. More...
 
static void dma_register_callback (struct dma_resource *resource, dma_callback_t callback, enum dma_callback_type type)
 Register a callback function for a dedicated DMA resource. More...
 
static void dma_reset_descriptor (struct dma_resource *resource)
 Reset DMA descriptor. More...
 
void dma_resume_job (struct dma_resource *resource)
 Resume a suspended DMA transfer. More...
 
enum status_code dma_start_transfer_job (struct dma_resource *resource)
 Start a DMA transfer. More...
 
void dma_suspend_job (struct dma_resource *resource)
 Suspend a DMA transfer. More...
 
static void dma_trigger_transfer (struct dma_resource *resource)
 Will set a software trigger for resource. More...
 
static void dma_unregister_callback (struct dma_resource *resource, enum dma_callback_type type)
 Unregister a callback function for a dedicated DMA resource. More...
 
static void dma_update_descriptor (struct dma_resource *resource, DmacDescriptor *descriptor)
 Update DMA descriptor. More...
 

Variables

DmacDescriptor descriptor_section [CONF_MAX_USED_CHANNEL_NUM]
 ExInitial description section. More...
 
uint8_t g_chan_interrupt_flag [CONF_MAX_USED_CHANNEL_NUM]
 

#define DMA_INVALID_CHANNEL   0xff

typedef void(* dma_callback_t)(struct dma_resource *const resource)

Type definition for a DMA resource callback function.

Address increment step size.

These bits select the address increment step size. The setting apply to source or destination address, depending on STEPSEL setting.

Enumerator
DMA_ADDRESS_INCREMENT_STEP_SIZE_1 

The address is incremented by (beat size * 1).

DMA_ADDRESS_INCREMENT_STEP_SIZE_2 

The address is incremented by (beat size * 2).

DMA_ADDRESS_INCREMENT_STEP_SIZE_4 

The address is incremented by (beat size * 4).

DMA_ADDRESS_INCREMENT_STEP_SIZE_8 

The address is incremented by (beat size * 8).

DMA_ADDRESS_INCREMENT_STEP_SIZE_16 

The address is incremented by (beat size * 16).

DMA_ADDRESS_INCREMENT_STEP_SIZE_32 

The address is incremented by (beat size * 32).

DMA_ADDRESS_INCREMENT_STEP_SIZE_64 

The address is incremented by (beat size * 64).

DMA_ADDRESS_INCREMENT_STEP_SIZE_128 

The address is incremented by (beat size * 128).

The basic transfer unit in DMAC is a beat, which is defined as a single bus access.

Its size is configurable and applies to both read and write.

Enumerator
DMA_BEAT_SIZE_BYTE 

8-bit access.

DMA_BEAT_SIZE_HWORD 

16-bit access.

DMA_BEAT_SIZE_WORD 

32-bit access.

Block action definitions.

Enumerator
DMA_BLOCK_ACTION_NOACT 

No action.

DMA_BLOCK_ACTION_INT 

Channel in normal operation and sets transfer complete interrupt flag after block transfer.

DMA_BLOCK_ACTION_SUSPEND 

Trigger channel suspend after block transfer and sets channel suspend interrupt flag once the channel is suspended.

DMA_BLOCK_ACTION_BOTH 

Sets transfer complete interrupt flag after a block transfer and trigger channel suspend.

The channel suspend interrupt flag will be set once the channel is suspended.

Callback types for DMA callback driver.

Enumerator
DMA_CALLBACK_TRANSFER_ERROR 

Callback for any of transfer errors.

A transfer error is flagged if a bus error is detected during an AHB access or when the DMAC fetches an invalid descriptor.

DMA_CALLBACK_TRANSFER_DONE 

Callback for transfer complete.

DMA_CALLBACK_CHANNEL_SUSPEND 

Callback for channel suspend.

DMA_CALLBACK_N 

Number of available callbacks.

DMA input actions.

Enumerator
DMA_EVENT_INPUT_NOACT 

No action.

DMA_EVENT_INPUT_TRIG 

Normal transfer and periodic transfer trigger.

DMA_EVENT_INPUT_CTRIG 

Conditional transfer trigger.

DMA_EVENT_INPUT_CBLOCK 

Conditional block transfer.

DMA_EVENT_INPUT_SUSPEND 

Channel suspend operation.

DMA_EVENT_INPUT_RESUME 

Channel resume operation.

DMA_EVENT_INPUT_SSKIP 

Skip next block suspend action.

Event output selection.

Enumerator
DMA_EVENT_OUTPUT_DISABLE 

Event generation disable.

DMA_EVENT_OUTPUT_BLOCK 

Event strobe when block transfer complete.

DMA_EVENT_OUTPUT_RESERVED 

Event output reserved.

DMA_EVENT_OUTPUT_BEAT 

Event strobe when beat transfer complete.

DMA priority level.

Enumerator
DMA_PRIORITY_LEVEL_0 

Priority level 0.

DMA_PRIORITY_LEVEL_1 

Priority level 1.

DMA_PRIORITY_LEVEL_2 

Priority level 2.

DMA_PRIORITY_LEVEL_3 

Priority level 3.

DMA step selection.

This bit determines whether the step size setting is applied to source or destination address.

Enumerator
DMA_STEPSEL_DST 

Step size settings apply to the destination address.

DMA_STEPSEL_SRC 

Step size settings apply to the source address.

DMA trigger action type.

Enumerator
DMA_TRIGGER_ACTION_BLOCK 

Perform a block transfer when triggered.

DMA_TRIGGER_ACTION_BEAT 

Perform a beat transfer when triggered.

DMA_TRIGGER_ACTION_TRANSACTION 

Perform a transaction when triggered.

void dma_abort_job ( struct dma_resource resource)

Abort a DMA transfer.

This function will abort a DMA transfer. The DMA channel used for the DMA resource will be disabled. The block transfer count will also be calculated and written to the DMA resource structure.

Note
The DMA resource will not be freed after calling this function. The function dma_free() can be used to free an allocated resource.
Parameters
[in,out]resourcePointer to the DMA resource

References Assert, dma_resource::channel_id, descriptor_section, DMA_INVALID_CHANNEL, dma_resource::job_status, STATUS_ABORTED, system_interrupt_enter_critical_section(), system_interrupt_leave_critical_section(), and dma_resource::transfered_size.

enum status_code dma_add_descriptor ( struct dma_resource resource,
DmacDescriptor *  descriptor 
)

Add a DMA transfer descriptor to a DMA resource.

This function will add a DMA transfer descriptor to a DMA resource. If there was a transfer descriptor already allocated to the DMA resource, the descriptor will be linked to the next descriptor address.

Parameters
[in]resourcePointer to the DMA resource
[in]descriptorPointer to the transfer descriptor
Return values
STATUS_OKThe descriptor is added to the DMA resource
STATUS_BUSYThe DMA resource was busy and the descriptor is not added

References dma_resource::descriptor, dma_resource::job_status, STATUS_BUSY, and STATUS_OK.

Referenced by configure_dma().

enum status_code dma_allocate ( struct dma_resource resource,
struct dma_resource_config config 
)

Allocate a DMA with configurations.

This function will allocate a proper channel for a DMA transfer request.

Parameters
[in,out]dma_resourcePointer to a DMA resource instance
[in]transfer_configConfigurations of the DMA transfer
Returns
Status of the allocation procedure.
Return values
STATUS_OKThe DMA resource was allocated successfully
STATUS_ERR_NOT_FOUNDDMA resource allocation failed

Perform a reset for the allocated channel

Configure the DMA control,channel registers and descriptors here

References _dma_active_resource, _dma_find_first_free_channel_and_allocate(), _dma_module::_dma_init, _dma_set_config(), Assert, dma_resource::channel_id, dma_resource::descriptor, descriptor_section, DMA_INVALID_CHANNEL, STATUS_ERR_NOT_FOUND, STATUS_OK, system_ahb_clock_set_mask(), system_apb_clock_set_mask(), SYSTEM_CLOCK_APB_APBB, system_interrupt_enter_critical_section(), and system_interrupt_leave_critical_section().

Referenced by configure_dma().

void dma_descriptor_create ( DmacDescriptor *  descriptor,
struct dma_descriptor_config config 
)
static void dma_descriptor_get_config_defaults ( struct dma_descriptor_config config)
inlinestatic

Initializes DMA transfer configuration with predefined default values.

This function will initialize a given DMA descriptor configuration structure to a set of known default values. This function should be called on any new instance of the configuration structure before being modified by the user application.

The default configuration is as follows:

  • Set the descriptor as valid
  • Disable event output
  • No block action
  • Set beat size as byte
  • Enable source increment
  • Enable destination increment
  • Step size is applied to the destination address
  • Address increment is beat size multiplied by 1
  • Default transfer size is set to 0
  • Default source address is set to NULL
  • Default destination address is set to NULL
  • Default next descriptor not available
    Parameters
    [out]configPointer to the configuration

Next descriptor address set to 0

References Assert, dma_descriptor_config::beat_size, dma_descriptor_config::block_action, dma_descriptor_config::block_transfer_count, dma_descriptor_config::descriptor_valid, dma_descriptor_config::destination_address, DMA_ADDRESS_INCREMENT_STEP_SIZE_1, DMA_BEAT_SIZE_BYTE, DMA_BLOCK_ACTION_NOACT, DMA_EVENT_OUTPUT_DISABLE, DMA_STEPSEL_DST, dma_descriptor_config::dst_increment_enable, dma_descriptor_config::event_output_selection, dma_descriptor_config::next_descriptor_address, dma_descriptor_config::source_address, dma_descriptor_config::src_increment_enable, dma_descriptor_config::step_selection, and dma_descriptor_config::step_size.

Referenced by configure_dma().

static void dma_disable_callback ( struct dma_resource resource,
enum dma_callback_type  type 
)
inlinestatic

Disable a callback function for a dedicated DMA resource.

Parameters
[in]resourcePointer to the DMA resource
[in]typeCallback function type

References Assert, dma_resource::callback_enable, and dma_resource::channel_id.

static void dma_enable_callback ( struct dma_resource resource,
enum dma_callback_type  type 
)
inlinestatic

Enable a callback function for a dedicated DMA resource.

Parameters
[in]resourcePointer to the DMA resource
[in]typeCallback function type

References Assert, dma_resource::callback_enable, and dma_resource::channel_id.

Referenced by configure_dma().

enum status_code dma_free ( struct dma_resource resource)

Free an allocated DMA resource.

This function will free an allocated DMA resource.

Parameters
[in,out]resourcePointer to the DMA resource
Returns
Status of the free procedure.
Return values
STATUS_OKThe DMA resource was freed successfully
STATUS_BUSYThe DMA resource was busy and can't be freed
STATUS_ERR_NOT_INITIALIZEDDMA resource was not initialized

References _dma_active_resource, _dma_release_channel(), _dma_module::allocated_channels, Assert, dma_resource::channel_id, DMA_INVALID_CHANNEL, dma_is_busy(), STATUS_BUSY, STATUS_ERR_NOT_INITIALIZED, STATUS_OK, system_interrupt_enter_critical_section(), and system_interrupt_leave_critical_section().

void dma_get_config_defaults ( struct dma_resource_config config)

Initializes config with predefined default values.

This function will initialize a given DMA configuration structure to a set of known default values. This function should be called on any new instance of the configuration structure before being modified by the user application.

The default configuration is as follows:

  • Software trigger is used as the transfer trigger
  • Priority level 0
  • Only software/event trigger
  • Requires a trigger for each transaction
  • No event input /output
  • DMA channel is disabled during sleep mode (if has the feature)
    Parameters
    [out]configPointer to the configuration

References Assert, DMA_EVENT_INPUT_NOACT, DMA_PRIORITY_LEVEL_0, DMA_TRIGGER_ACTION_TRANSACTION, dma_resource_config::event_config, dma_events_config::event_output_enable, dma_events_config::input_action, dma_resource_config::peripheral_trigger, dma_resource_config::priority, and dma_resource_config::trigger_action.

Referenced by configure_dma().

static enum status_code dma_get_job_status ( struct dma_resource resource)
inlinestatic

Get DMA resource status.

Parameters
[in]resourcePointer to the DMA resource
Returns
Status of the DMA resource.

References Assert, and dma_resource::job_status.

static bool dma_is_busy ( struct dma_resource resource)
inlinestatic

Check if the given DMA resource is busy.

Parameters
[in]resourcePointer to the DMA resource
Returns
Status which indicates whether the DMA resource is busy.
Return values
trueThe DMA resource has an on-going transfer
falseThe DMA resource is not busy

References Assert, dma_resource::job_status, and STATUS_BUSY.

Referenced by dma_free().

static void dma_register_callback ( struct dma_resource resource,
dma_callback_t  callback,
enum dma_callback_type  type 
)
inlinestatic

Register a callback function for a dedicated DMA resource.

There are three types of callback functions, which can be registered:

  • Callback for transfer complete
  • Callback for transfer error
  • Callback for channel suspend
Parameters
[in]resourcePointer to the DMA resource
[in]callbackPointer to the callback function
[in]typeCallback function type

References Assert, and dma_resource::callback.

Referenced by configure_dma().

static void dma_reset_descriptor ( struct dma_resource resource)
inlinestatic

Reset DMA descriptor.

This function will clear the DESCADDR register of an allocated DMA resource.

References Assert, and dma_resource::descriptor.

void dma_resume_job ( struct dma_resource resource)

Resume a suspended DMA transfer.

This function try to resume a suspended transfer of a DMA resource.

Parameters
[in]resourcePointer to the DMA resource

References Assert, dma_resource::channel_id, DMA_INVALID_CHANNEL, dma_resource::job_status, MAX_JOB_RESUME_COUNT, STATUS_BUSY, STATUS_ERR_TIMEOUT, STATUS_SUSPEND, system_interrupt_enter_critical_section(), and system_interrupt_leave_critical_section().

enum status_code dma_start_transfer_job ( struct dma_resource resource)

Start a DMA transfer.

This function will start a DMA transfer through an allocated DMA resource.

Parameters
[in,out]resourcePointer to the DMA resource
Returns
Status of the transfer start procedure.
Return values
STATUS_OKThe transfer was started successfully
STATUS_BUSYThe DMA resource was busy and the transfer was not started
STATUS_ERR_INVALID_ARGTransfer size is 0 and transfer was not started

References Assert, dma_resource::channel_id, dma_resource::descriptor, descriptor_section, DMA_INVALID_CHANNEL, g_chan_interrupt_flag, dma_resource::job_status, STATUS_BUSY, STATUS_ERR_INVALID_ARG, STATUS_OK, system_interrupt_enable(), system_interrupt_enter_critical_section(), system_interrupt_leave_critical_section(), and SYSTEM_INTERRUPT_MODULE_DMA.

Referenced by configure_dma(), and test_standby_mode_dynamic_power_sleepwalking().

void dma_suspend_job ( struct dma_resource resource)

Suspend a DMA transfer.

This function will request to suspend the transfer of the DMA resource. The channel is kept enabled, can receive transfer triggers (the transfer pending bit will be set), but will be removed from the arbitration scheme. The channel operation can be resumed by calling dma_resume_job().

Note
This function sets the command to suspend the DMA channel associated with a DMA resource. The channel suspend interrupt flag indicates whether the transfer is truly suspended.
Parameters
[in]resourcePointer to the DMA resource

References Assert, dma_resource::channel_id, DMA_INVALID_CHANNEL, system_interrupt_enter_critical_section(), and system_interrupt_leave_critical_section().

static void dma_trigger_transfer ( struct dma_resource resource)
inlinestatic

Will set a software trigger for resource.

This function is used to set a software trigger on the DMA channel associated with resource. If a trigger is already pending no new trigger will be generated for the channel.

Parameters
[in]resourcePointer to the DMA resource

References Assert, and dma_resource::channel_id.

static void dma_unregister_callback ( struct dma_resource resource,
enum dma_callback_type  type 
)
inlinestatic

Unregister a callback function for a dedicated DMA resource.

There are three types of callback functions:

  • Callback for transfer complete
  • Callback for transfer error
  • Callback for channel suspend

The application can unregister any of the callback functions which are already registered and are no longer needed.

Parameters
[in]resourcePointer to the DMA resource
[in]typeCallback function type

References Assert, and dma_resource::callback.

static void dma_update_descriptor ( struct dma_resource resource,
DmacDescriptor *  descriptor 
)
inlinestatic

Update DMA descriptor.

This function can update the descriptor of an allocated DMA resource.

References Assert, and dma_resource::descriptor.

DmacDescriptor descriptor_section[CONF_MAX_USED_CHANNEL_NUM]

ExInitial description section.

Referenced by dma_abort_job(), dma_allocate(), dma_start_transfer_job(), and DMAC_Handler().

uint8_t g_chan_interrupt_flag[CONF_MAX_USED_CHANNEL_NUM]

Referenced by dma_start_transfer_job().