[PATCH net-next V4 0/3] net: axienet: Introduce dmaengine

[Sarath Babu Naidu Gaddam]

The axiethernet driver can use the dmaengine framework to communicate
with the xilinx DMAengine driver(AXIDMA, MCDMA). The inspiration behind
this dmaengine adoption is to reuse the in-kernel xilinx dma engine
driver[1] and remove redundant dma programming sequence[2] from the
ethernet driver. This simplifies the ethernet driver and also makes
it generic to be hooked to any complaint dma IP i.e AXIDMA, MCDMA
without any modification.

The dmaengine framework was extended for metadata API support during
the axidma RFC[3] discussion. However, it still needs further
enhancements to make it well suited for ethernet usecases.

Backward compatibility support:
To support backward compatibility, we are planning to use below approach,
1) Use "dmas" property as an optional for now to differentiate
   dmaengine based ethernet Driver or built-in dma ethernet driver.
   Will move this property to required property some time later.
2) after some time, will introduce a new compatible string to support
   the dmaengine method, This new compatible name will use different
   APIs for init and data transfer.

Comments, suggestions, thoughts to implement remaining functional
features are very welcome!

[1]: https://github.com/torvalds/linux/blob/master/drivers/dma/xilinx/xilinx_dma.c
[2]: https://github.com/torvalds/linux/blob/master/drivers/net/ethernet/xilinx/xilinx_axienet_main.c#L238
[3]: http://lkml.iu.edu/hypermail/linux/kernel/1804.0/00367.html

Changes in V4:
1) Updated commit description about tx/rx channels name(1/3).
2) Removed "dt-bindings" and "dmaengine" strings in subject(1/3).
3) Extended dmas and dma-names to support MCDMA channel names(1/3).
4) Rename has_dmas to use_dmaegine(2/3).
5) Remove the AXIENET_USE_DMA(2/3).
6) Remove the AXIENET_USE_DMA(3/3).
7) Add dev_err_probe for dma_request_chan error handling(3/3).
8) Add kmem_cache_destroy for create in axienet_setup_dma_chan(3/3).

Changes in V3:
1) Moved RFC to PATCH.
2) Removed ethtool get/set coalesce, will be added later.
3) Added backward comapatible support.
4) Split the dmaengine support patch of V2 into two patches(2/3 and 3/3).
https://lore.kernel.org/all/20220920055703.13246-4-sarath.babu.naidu.gaddam@xxxxxxx/

Changes in V2:
1) Add ethtool get/set coalesce and DMA reset using DMAengine framework.
2) Add performance numbers.
3) Remove .txt and change the name of file to xlnx,axiethernet.yaml.
4) Fix DT check warning(Fix DT check warning('device_type' does not match
   any of the regexes:'pinctrl-[0-9]+' From schema: Documentation/
   devicetree/bindings/net/xilinx_axienet.yaml).

Radhey Shyam Pandey (1):
  dt-bindings: net: xlnx,axi-ethernet: Introduce DMA support

Sarath Babu Naidu Gaddam (2):
  net: axienet: Preparatory changes for dmaengine support
  net: axienet: Introduce dmaengine support

 .../bindings/net/xlnx,axi-ethernet.yaml       |  16 +
 drivers/net/ethernet/xilinx/Kconfig           |   1 +
 drivers/net/ethernet/xilinx/xilinx_axienet.h  |   8 +
 .../net/ethernet/xilinx/xilinx_axienet_main.c | 616 ++++++++++++++----
 4 files changed, 516 insertions(+), 125 deletions(-)

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2.25.1