DMA

Functions
int	FlxCard::dma_max_tlp_bytes ()
void	FlxCard::dma_to_host (u_int dma_id, u_long dst, size_t size, u_int flags)
void	FlxCard::dma_from_host (u_int dma_id, u_long src, size_t size, u_int flags)
bool	FlxCard::dma_enabled (u_int dma_id)
void	FlxCard::dma_wait (u_int dma_id)
void	FlxCard::dma_stop (u_int dma_id)
void	FlxCard::dma_advance_ptr (u_int dma_id, u_long dst, size_t size, size_t bytes)
void	FlxCard::dma_set_ptr (u_int dma_id, u_long dst)
u_long	FlxCard::dma_get_ptr (u_int dma_id)
u_long	FlxCard::dma_get_read_ptr (u_int dma_id)
void	FlxCard::dma_reset ()
u_long	FlxCard::dma_get_fw_ptr (u_int dma_id)
u_long	FlxCard::dma_get_current_address (u_int dma_id)
bool	FlxCard::dma_cmp_even_bits (u_int dma_id)

Detailed Description

A set of functions to setup, start and stop DMA transfers and to interact with the circular buffer PC pointers.

Function Documentation

dma_max_tlp_bytes()

int FlxCard::dma_max_tlp_bytes ( )

inline

Calls the flx driver in order to determine the maximum number of TLP bytes that the H/W can support.

Errors In case of an error, an exception is thrown.

dma_to_host()

void FlxCard::dma_to_host	(	u_int	dma_id,
		u_long	dst,
		size_t	size,
		u_int	flags )

First stops the DMA channel identified by dma_id. It does not check if the channel is busy. Then it programs the channel and starts a new DMA from-device-to-host operation.

Note: The bits 10:0 of the DMA descriptor (bitfield NUM_WORDS in the Wupper documentation) will be set to the maximum TLP size supported by the system. Therefore, the transfer size has to be a multiple of that value.

Errors In case of an error, an exception is thrown.

Parameters

dma_id	The DMA channel (descriptor) to be used; valid numbers are 0..7
dst	The value for the start_address field of the descriptor. NOTE: You have to provide a physical memory address
size	The size of the transfer in bytes
flags	The value for the wrap_around field of the descriptor; "1" means: enable wrap around, i.e. use continuous DMA

dma_from_host()

void FlxCard::dma_from_host	(	u_int	dma_id,
		u_long	src,
		size_t	size,
		u_int	flags )

First stops the DMA channel identified by dma_id. It does not check if the channel is busy. Then it programs the channel and starts a new DMA from-host-to-device operation.

Note: The size of the transfer has to be a multiple of 32 bytes.

The method internally computes the optimal value for the bits 10:0 of the DMA descriptor (bitfield NUM_WORDS in the Wupper documentation).

The algorithm used is this:

1. if transfersize % 32 != 0: error("number of bytes transferred must be a multiple of 32")
2. tlp = get_max_tlp()
3. if transfersize % tlp == 0: do transfer
4. else: tlp = tlp >> 1 && goto 3

Note: The algorithm above is currently not used: the transfer unit size is set to the minimum of 32 bytes, to make sure small messages are always sent, in particular when continuous DMA is enabled. The upper 16 bits of the flags parameter can be used to force a transfer size unequal to (so larger than) 32 bytes (but must be a multiple of 32).

Errors In case of an error, an exception is thrown.

Parameters

dma_id	The DMA channel (descriptor) to be used; valid numbers are 0..7
src	The value for the start_address field of the descriptor. NOTE: You have to provide a physical memory address
size	The size of the transfer in bytes
flags	The value for the wrap_around field of the descriptor. “1” means: enable wrap around, i.e. use continuous DMA

dma_enabled()

bool FlxCard::dma_enabled

(

u_int

dma_id

)

Returns whether the DMA channel identified by dma_id is enabled or not.

Parameters

dma_id

The DMA channel (descriptor) to be used; valid numbers are 0..7

dma_wait()

void FlxCard::dma_wait

(

u_int

dma_id

)

Is blocking. It returns once the DMA on channel dma_id has ended. The method has an internal (hard wired) time out of 1 second.

Errors In case the DMA has not ended after 1 second an exception is thrown.

Parameters

dma_id

The DMA channel (descriptor) to be used; valid numbers are 0..7

dma_stop()

void FlxCard::dma_stop

(

u_int

dma_id

)

Clears the DMA channel identified by dma_id. It does not check the status of that channel.

Parameters

dma_id

The DMA channel (descriptor) to be used; valid numbers are 0..7

dma_advance_ptr()

void FlxCard::dma_advance_ptr	(	u_int	dma_id,
		u_long	dst,
		size_t	size,
		size_t	bytes )

Advances the internal read pointer of the DMA channel by the number of bytes given. This is used when operating the DMA engine in "endless DMA" / "circular buffer" mode. This method is to be called by the user after processing data at the head of the circular buffer to free the buffer for DMA writes or reads of the FLX card again.

Parameters

dma_id	The DMA channel (descriptor) to be used; valid numbers are 0..7
dst	See below. NOTE: You have to provide a physical memory address
size	If the value of the read_ptr field, after adding bytes is larger than dst + size, size will be subtracted from read_ptr
bytes	This value will be added to the read_ptr field of the DMA descriptor

dma_set_ptr()

void FlxCard::dma_set_ptr	(	u_int	dma_id,
		u_long	dst )

Directly writes the read pointer of a DMA channel.

Parameters

dma_id	The DMA channel (descriptor) to be used; valid numbers are 0..7
dst	The read pointer register of the DMA channel will be set to the value in dst

dma_get_ptr()

u_long FlxCard::dma_get_ptr

(

u_int

dma_id

)

Returns the current value of the SW_POINTER. That is to say the bits 127:64 of the DMA_DESC_[0..7]a as defined in the Wupper documentation.

Parameters

dma_id

The DMA channel (descriptor) to be used; valid numbers are 0..7

dma_reset()

void FlxCard::dma_reset

(

)

Triggers a reset by the DMA_RESET register in BAR0.

dma_get_fw_ptr()

u_long FlxCard::dma_get_fw_ptr

(

u_int

dma_id

)

Reads the status register of a DMA descriptor (i.e. one of the DMA_DESC_STATUS_* registers) and returns the value of the FW_POINTER bit field (bits 63:0).

Parameters

dma_id

The DMA channel (descriptor) to be queried; valid numbers are 0..7

dma_cmp_even_bits()

bool FlxCard::dma_cmp_even_bits

(

u_int

dma_id

)

Reads the even_addr_dma and even_pc_dma bits of a DMA channel and compares them.

Parameters

dma_id

The DMA channel (descriptor) to be used; valid numbers are 0..7

Returns

Returns true if the bits have the same value and false if not.