[PATCH v4 0/2] spi: support devices with no wire in one direction

[Cole Munz <Munzzyy1@proton.me>]

The Flipper One display bus has no MISO wire; the pin is the
end-of-frame GPIO. Patch 1 maps spi-{tx,rx}-bus-width = <0> to
SPI_NO_TX/SPI_NO_RX and validates transfers against the bits in
dm_spi_xfer(). Patch 2 has the Rockchip driver pick its transfer mode
from them so the unused FIFO stays out of the transfer. Background is
in the v2 cover letter:

https://lore.kernel.org/all/cover.1787238071.git.Munzzyy1@proton.me/

Changes in v4, both from the comment discussion with Quentin:
- toread comment cut down to the one factual sentence
- the comment above rkspi_wait_till_not_busy() now says why the wait
  matters: the TX FIFO can still hold unsent data and disabling the
  controller clears the FIFOs
- patch 1 unchanged, carries the Acked-by

Cole Munz (2):
  spi: Handle spi-{tx,rx}-bus-width 0 as SPI_NO_TX/SPI_NO_RX
  spi: rockchip: skip the unused FIFO direction on a one-wire device

 drivers/spi/rk_spi.c     | 33 ++++++++++++++++++++++++++-------
 drivers/spi/spi-uclass.c | 16 ++++++++++++++++
 include/spi.h            |  2 ++
 test/dm/spi.c            | 39 +++++++++++++++++++++++++++++++++++++++
 4 files changed, 83 insertions(+), 7 deletions(-)


base-commit: 527115ef6783cec49e5610c523c124b399011361
-- 
2.55.0