Re: [PATCH 0/9] dmaengine: Support bus widths of 32 bytes and above

["Nuno Sá" <noname.nuno@gmail.com>]

On Thu, Jul 30, 2026 at 02:05:43PM -0500, Frank Li wrote:
> On Thu, Jul 30, 2026 at 03:23:07PM +0100, Nuno Sá via B4 Relay wrote:
> > [You don't often get email from devnull+nuno.sa.analog.com@kernel.org. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> >
> > 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 bitmap
> > based bus width capabilities. The legacy dma_device u32 fields are kept
> > for now so the remaining DMA controller drivers can be converted
> > incrementally. dma_get_slave_caps() folds legacy producer masks into the
> > new bitmap representation returned to consumers.
> >
> > 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 v1:
> 
> this should be v2, RFC is v1

Ups! Sorry about that! But I guess now we keep this path? I mean, I
should not bump to v3 next right?

- Nuno Sá

> 
> Frank
> > - Drop RFC tag.
> > - Rename the new capability representation and helpers from address
> >   width terminology to bus width terminology.
> > - Convert all current dma_get_slave_caps() consumers that used the
> >   legacy src/dst_addr_widths fields.
> > - Convert a small set of DMA controller producers and the stm32-dma3
> >   per-channel capability callback.
> > - Add helper documentation for the new public API.
> > - Link to RFC: https://lore.kernel.org/dmaengine/20260616-dmaengine-support-wider-dma-masks-v1-0-da23a8dcb756@analog.com/
> >
> > ---
> > Nuno Sá (9):
> >       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                         |  13 +-
> >  drivers/dma/dmaengine.c                            |  20 +-
> >  drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c     |  39 ++--
> >  drivers/dma/qcom/gpi.c                             |  11 +-
> >  drivers/dma/stm32/stm32-dma3.c                     |  32 +--
> >  drivers/iio/buffer/industrialio-buffer-dmaengine.c |  15 +-
> >  drivers/spi/spi-dw-dma.c                           |   6 +-
> >  drivers/spi/spi-dw.h                               |   3 +-
> >  include/linux/dmaengine.h                          | 234 ++++++++++++++++++++-
> >  sound/core/pcm_dmaengine.c                         |  14 +-
> >  10 files changed, 323 insertions(+), 64 deletions(-)
> > ---
> > base-commit: 7524fe142b5a772f8421aeee2132cf7e21a00103
> > change-id: 20260615-dmaengine-support-wider-dma-masks-5aac12497e27
> > --
> >
> > Thanks!
> > - Nuno Sá
> >
> >