Update dma.py

[mstojke]

Added argument for _SGDMAChannel.transfer() method to write BD's to selected memory (for example: in case when buffer descriptors will be stored in PL RAM)

Signed-off-by: Michał Stojke michal.stojke@pwr.edu.pl

[jogomojo]

Hi @mstojke, thank you for your PR.

In what context have you used your updated code?

From what I can see, you add bd_allocate_target to PYNQ's allocate function as a target. However, allocate expects target to be a Device class (e.g. XrtDevice), which then calls the device's own allocate function (e.g. XrtDevice.allocate)

PYNQ/pynq/buffer.py

Lines 138 to 158 in 19ed17d

	def allocate(shape, dtype="u4", target=None, **kwargs):
	"""Allocate a PYNQ buffer
	This API mimics the numpy ndarray constructor with the following
	differences:
	* The default dtype is 32-bit unsigned int rather than float
	* A new ``target`` keyword parameter to determine where the
	buffer should be allocated
	The target determines where the buffer gets allocated
	* If None then the currently active device is used
	* If a Device is specified then the main memory
	"""
	from .pl_server import Device
	if target is None:
	target = Device.active_device
	return target.allocate(shape, dtype, **kwargs)

[mstojke]

Hi @jogomojo

I made a mistake in the description of the transfer() function in the _SGDMAChannel() class. It should actually pass a memory device instead of the described PynqBuffer.

PYNQ/pynq/lib/dma.py

Lines 348 to 350 in e35a668

	bd_allocate_target : PynqBuffer
	The target memory to allocate buffer descriptors. Default is None.
	If None, the buffer descriptors are allocated in the active memory.

I used the modified code to allocate memory space in the PL DDR4. Below is a fragment from my project showing how it was used.

dma_max_transfer_size = 4194304 * 4
overlay.dma = DMA(overlay.ip_dict['axi_dma_0'])
overlay.dma.recvchannel._max_size = dma_max_transfer_size 
overlay.dma.recvchannel.transfer(buf, ddr_4_target=overlay.ddr4_0)

[jogomojo]

Hi @mstojke

Could you share a minimal Vivado tcl design I could build and a Python file for me to run so I can test this out?

[mstojke]

Hi @jogomojo

I added you to the repository with the project.