add support for Mediatek High-Speed DMA controller on MT7622 and MT7623 SoC

From: Sean Wang <[email protected]>

Changes since v6:
- add Reviewed-by tag from Rob to patch 1

Changes since v5:
- use C99 style comments at the first two lines
- remove unused header includes
- use directly KBUILD_MODNAME as a driver name
- use DMA_SLAVE_BUSWIDTH_4_BYTES to reflect the real bus width
- refine comments
- refine code style aligning with 80 chars and wrap
- use GFP_NOWAIT as the flag for memory allocations for DMA
- changing flow for it should be returning 0 instead of -ENOSPC for all successful descriptor issuing either in part or in full
- refine ISR with a fail-safe loop, and having a status check at the start
- remove a few unused code
- refine callback device_terminate_all, which does it should be freeing all descriptors
- refine callback device_free_chan_resources, which does it should be freeing all descriptors before freeing physical channel
- remove unnecessary callback device_synchronize

Changes since v4:
- rebase to 4.16-rc1
- fold back patch 4 and 5 in v4 into the original commit
- add the missing header included
- fix typo and add more explanation in existing comments
- fix the comments with kernel-doc style which uses /** as the begin
- begin the multi-line comments with /*

Changes since v3:
- enhance dt-binding documents based on Rob's comments
- make consistent among all comments
- perfer ordering declarations longest to shortest
- fix warning reported from kbuild test robot
- add patch 4 and 5 to keep Fengguang and Julia's effort

Changes since v2:
- remove extra tasklets and refactor driver for letting descriptors being processed ASAP.
- add more comments stating the relevant logic
- remove unused macro and variables
- change to use the disclaimer with SPDX identifier
- add mt7622 support
- refine hardware initialization sequence
- add tx_status support for DMA_RESIDUE_GRANULARITY_SEGMENT
- refine remove handler with killing vc's tasklet

Changes since v1:
- fix typo in the commit message.
- delete status shown in the dt-binding example.

This patchset introduces support for MediaTek High-Speed DMA controller (MTK-HSDMA) Currently, the driver is already tested successfully with dmatest module on MT7622 and MT7623 SoC.

MTK-HSDMA on MT7622/23 SoC has a single ring which is dedicated for doing memory-to-memory transfer through ring-based descriptor management. Even though there is only a single ring available inside HSDMA, the driver is being extended to the support for multiple virtual channels processing simultaneously by means of DMA_VIRTUAL_CHANNELS.

Sean Wang (3):
dt-bindings: dmaengine: Add MediaTek High-Speed DMA controller
bindings
dmaengine: mediatek: Add MediaTek High-Speed DMA controller for MT7622

    and MT7623 SoC

dmaengine: mediatek: update MAINTAINERS entry with MediaTek DMA driver

 .../devicetree/bindings/dma/mtk-hsdma.txt          |   33 +
 MAINTAINERS                                        |    9 +
 drivers/dma/Kconfig                                |    2 +
 drivers/dma/Makefile                               |    1 +
 drivers/dma/mediatek/Kconfig                       |   13 +
 drivers/dma/mediatek/Makefile                      |    1 +
 drivers/dma/mediatek/mtk-hsdma.c                   | 1056 ++++++++++++++++++++
 7 files changed, 1115 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/dma/mtk-hsdma.txt
 create mode 100644 drivers/dma/mediatek/Kconfig
 create mode 100644 drivers/dma/mediatek/Makefile
 create mode 100644 drivers/dma/mediatek/mtk-hsdma.c

2.7.4