[PATCH v2 0/9] iio: adc: rzt2h: add DMA buffer support

[Cosmin Tanislav]

Add DMA-based buffered capture to the Renesas RZ/T2H and RZ/N2H ADC
driver and the necessary device-tree properties. Also add a per-channel
sampling-frequency control.

Capture uses a cyclic DMA transfer into a non-coherent buffer. The DMA
controller has no per-descriptor scatter-gather and each transfer needs
to be of power-of-two width, so the transfer covers the smallest
power-of-two-aligned group of channel registers spanning the enabled
channels, and a consumer kthread compacts each completed period down to
the enabled channels before handing it to the IIO core.

V2:
 * advance period index on backlog overflow
 * add a comment describing the logic for dropping already overwritten
   periods
 * build dma_slave_config as a compound literal
 * use the local dev instead of adc->dev in rzt2h_adc_setup_dma()
 * sync the DMA buffer to device immediately after allocation to handle
   the zero-fill done by the CPU
 * extend the single read completion timeout to maximum possible
   conversion time + 1 jiffy
 * pick up Conor's Acked-by

Cosmin Tanislav (9):
  iio: adc: rzt2h: remove unused struct rzt2h_adc::max_channels
  iio: adc: rzt2h: store IRQ in private state
  iio: adc: rzt2h: store the physical address in private state
  iio: adc: rzt2h: claim direct mode on single reads
  iio: adc: rzt2h: implement DMA buffer support
  iio: adc: rzt2h: expose sampling frequency
  dt-bindings: iio: adc: renesas,r9a09g077-adc: document DMA support
  arm64: dts: renesas: r9a09g077: Wire up DMA support for ADC
  arm64: dts: renesas: r9a09g087: Wire up DMA support for ADC

 .../iio/adc/renesas,r9a09g077-adc.yaml        |  12 +
 arch/arm64/boot/dts/renesas/r9a09g077.dtsi    |   6 +
 arch/arm64/boot/dts/renesas/r9a09g087.dtsi    |   6 +
 drivers/iio/adc/Kconfig                       |   2 +
 drivers/iio/adc/rzt2h_adc.c                   | 499 +++++++++++++++++-
 5 files changed, 509 insertions(+), 16 deletions(-)

-- 
2.55.0