# Xilinx AXI DMA configuration options

# Copyright (c) 2023 CISPA Helmholtz Center for Information Security gGmbH
# SPDX-License-Identifier: Apache-2.0

config DMA_XILINX_AXI_DMA
	bool "Xilinx AXI DMA LogiCORE IP driver"
	default y
	depends on DT_HAS_XLNX_AXI_DMA_1_00_A_ENABLED || DT_HAS_XLNX_ETH_DMA_ENABLED
	help
	  DMA driver for Xilinx AXI DMAs, usually found on FPGAs.


config DMA_XILINX_AXI_DMA_DISABLE_CACHE_WHEN_ACCESSING_SG_DESCRIPTORS
	bool "Disable data cache while accessing Scatter-Gather Descriptors."
	depends on DMA_XILINX_AXI_DMA
	default n
	help
		Disable dcache while operating on Scatter-Gather descriptors.
		This allows the DMA to be used on architectures that do not provide
		coherency for DMA accesses. If you are unsure whether you need this feature,
		you should select n here.

config DMA_XILINX_AXI_DMA_SG_DESCRIPTOR_NUM_TX
	int "Number of transfer descriptors allocated for transmission (TX)."
	depends on DMA_XILINX_AXI_DMA
	default 16
	help
		The Xilinx AXI DMA uses a ring of in-memory DMA descriptors which reference
		the buffers containing the network packets and control and status information.
		Increasing the number of descriptors increases the amount of packets in flight,
		which benefits performance, while increasing memory usage.

config DMA_XILINX_AXI_DMA_SG_DESCRIPTOR_NUM_RX
	int "Number of transfer descriptors allocated for reception (RX)."
	depends on DMA_XILINX_AXI_DMA
	default 16
	help
		The AXI DMA driver currently allocates a single DMA descriptor for each RX transfer,
		because transfers need to be started by the upstream driver.

choice
	prompt "IRQs to lock when manipulating per-channel data structures during dma_start."
	depends on DMA_XILINX_AXI_DMA
	default DMA_XILINX_AXI_DMA_LOCK_ALL_IRQS

config DMA_XILINX_AXI_DMA_LOCK_ALL_IRQS
	bool "Lock all IRQs"
	help
		Lock all interrupts (including, e.g., timers and scheduler) when modifying channel data
		during dma_start.
		This is required when calling dma_start outside of the TX/RX callbacks.
		This is the safest option and the default, select this if you are unsure.

config DMA_XILINX_AXI_DMA_LOCK_DMA_IRQS
	bool "Lock TX and RX IRQs"
	help
		Lock all interrupts of this DMA device when modifying channel data during dma_start.
		This is only safe when dma_start is only called from the TX/RX callbacks (and possibly
		once directly after initialization of the DMA).

config DMA_XILINX_AXI_DMA_LOCK_CHANNEL_IRQ
	bool "Lock IRQs of the DMA channel"
	help
		Only lock the interrupt of the DMA channel whose data are to be modified during dma_start.
		Only select this when you can guarantee that dma_start is only called from the callback
		registered for the same channel.

endchoice

config DMA_XILINX_AXI_DMA_POLL_INTERVAL
	int "Period of the timer used for polling the DMA in milliseconds"
	depends on DMA_XILINX_AXI_DMA
	default 100
	help
		On certain platforms (e.g., RISC-V), the DMA driver can sometimes miss interrupts.
		This can cause the DMA driver to stop processing completed transactions.
		In order to prevent this, the DMA driver periodically polls the DMA's registers and
		determines whether it needs to handle outstanding transactions.
		This configuration controls how often this happens.
		Choose a larger value to minimize overhead and a smaller value to minimize
		worst-case latency.

config DMA_XILINX_AXI_DMA_INTERRUPT_THRESHOLD
	int "Number of completed transactions after which to trigger an interrupt"
	depends on DMA_XILINX_AXI_DMA
	range 1 255
	default 8
	help
		Number of completed transactions after which to trigger an interrupt.
		Decrease to minimize latency, increase to minimize overhead introduced by interrupts.

config DMA_XILINX_AXI_DMA_INTERRUPT_TIMEOUT
	int "Timeout for triggering an interrupt"
	depends on DMA_XILINX_AXI_DMA
	range 0 255
	default 16
	help
		Trigger an interrupt at the latest after
		CONFIG_DMA_XILINX_AXI_DMA_INTERRUPT_TIMEOUT * 125 * DMA_CLOCK_PERIOD cycles.
		This is useful in conjunction with DMA_XILINX_AXI_DMA_INTERRUPT_THRESHOLD - the DMA
		can raise an interrupt before the threshold is reached, minimizing latency in scenarios
		where only few transactions per second are completed.
		Set to 0 to disable this feature, i.e., interrupts will only be raised when the threshold
		has been reached.