[PATCH v4 00/10] dmaengine: Support bus widths of 32 bytes and above

[Nuno Sá]

The DMA engine slave capabilities advertise the supported source and
destination bus widths through src_addr_widths / dst_addr_widths. These
are plain u32 bitmasks where a set bit's position equals the
corresponding enum dma_slave_buswidth value, e.g.
DMA_SLAVE_BUSWIDTH_4_BYTES sets bit 4.

The consequence is that widths of 32 bytes and above cannot be
represented at all: DMA_SLAVE_BUSWIDTH_32/64/128_BYTES would need bits
32, 64 and 128, which do not fit in a u32. Hardware with wider data
paths is becoming common, so add a representation that can express these
widths while still using enum dma_slave_buswidth.

This series switches consumers and a small set of producers to the new
bus width capabilities, represented by a dma_buswidth_mask_t modeled
after dma_cap_mask_t. The legacy dma_device u32 fields are kept for now
so the remaining DMA controller drivers can be converted incrementally:
dma_async_device_register() folds a legacy-only producer's u32 into the
mask, so consumers only ever have to look at the mask.

The new interface lives in include/linux/dma/engine/{types,widthmask}.h
rather than in linux/dmaengine.h, so that only its users pay for the
linux/bitmap.h include. Every accessor takes a dma_buswidth_mask_t,
which means the interface will not change when the legacy fields are
eventually dropped.

Once the remaining producers are converted, the legacy dma_device
src/dst_addr_widths fields can be removed as a final cleanup.

This issue was discussed before here:

https://lore.kernel.org/dmaengine/abkoXXbaxaiqbBuX@vaman/

Changes in v4:
- Patch 1 (new):
  - Split out of the old patch 1: move enum dma_slave_buswidth into the
    new include/linux/dma/engine/types.h, with no other change (Andy).
  - While at it, add the missing kernel-doc for the enum members, which
    kernel-doc warned about already before this series, and describe the
    UNDEFINED case (Andy).
- Patch 2:
  - Fold the bus width masks in both directions in
    dma_async_device_register(). A producer already converted only fills
    in the mask, so the legacy u32 stayed zero and the consumers not
    converted yet ended up with no bus width at all: IIO fell back to a
    width of 1 and spi-dw disabled DMA entirely. Derive the legacy u32
    from the mask so every intermediate commit of this series keeps
    working (sashiko-bot). Dropped again in the last patch.
  - widthmask.h: include linux/errno.h and group the generic linux/*.h
    includes before the subsystem ones (Andy).
  - Split declaration and assignment in __dma_bus_width_min() (Andy).
  - Group linux/dma/engine/types.h after the generic includes in
    linux/dmaengine.h (Andy).
  - Drop the include/linux/dma/engine/ MAINTAINERS entry, as
    include/linux/dma/ already matches recursively (Andy).
  - Drop bitops.h include (Andy).
- Patch 3, 4, 5, 7:
  - Fix the helper names in the commit messages, which still referred to
    the v2 interface (sashiko-bot).
- Patch 6:
  - Drop the claim about an unvalidated device tree bus width from the
    commit message, as sdw/ddw do not come from the device tree
    (Amelie).
- Patch 9:
  - Sort the new linux/dma/engine/types.h include in spi-dw.h (Andy).
- Link to v3: https://patch.msgid.link/20260831-dmaengine-support-wider-dma-masks-v3-0-507d97496f2d@xxxxxxxxxx

---
Nuno Sá (10):
      dmaengine: Move enum dma_slave_buswidth to a new header
      dmaengine: Support bus widths of 32 bytes and above
      dmaengine: dma-axi-dmac: Use bus width capability helpers
      dmaengine: dw-axi-dmac: Use bus width capability helpers
      dmaengine: qcom: gpi: Use bus width capability helpers
      dmaengine: stm32-dma3: Use bus width capability helpers
      iio: buffer-dmaengine: Use dma_slave_caps bus width accessors
      ALSA: pcm_dmaengine: Use dma_slave_caps bus width helpers
      spi: dw: Use dma_slave_caps bus width helpers
      dmaengine: Drop legacy bus width fields from dma_slave_caps

 drivers/dma/dma-axi-dmac.c                         |  14 +-
 drivers/dma/dmaengine.c                            |  25 +++-
 drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c     |  38 +++--
 drivers/dma/qcom/gpi.c                             |  12 +-
 drivers/dma/stm32/stm32-dma3.c                     |  34 +++--
 drivers/iio/buffer/industrialio-buffer-dmaengine.c |  16 +-
 drivers/spi/spi-dw-dma.c                           |   8 +-
 drivers/spi/spi-dw.h                               |   3 +-
 include/linux/dma/engine/types.h                   |  55 +++++++
 include/linux/dma/engine/widthmask.h               | 166 +++++++++++++++++++++
 include/linux/dmaengine.h                          |  49 +++---
 sound/core/pcm_dmaengine.c                         |  21 ++-
 12 files changed, 357 insertions(+), 84 deletions(-)
---
base-commit: 0613e7934ee233d726af8d8c89f251a1c4df738d
change-id: 20260615-dmaengine-support-wider-dma-masks-5aac12497e27
--

Thanks!
- Nuno Sá