spi: add SPI_MOSI_IDLE_LOW mode bit

Some spi controller switch the mosi line to high, whenever they are
idle. This may not be desired in all use cases. For example neopixel
leds can get confused and flicker due to misinterpreting the idle state.
Therefore, we introduce a new spi-mode bit, with which the idle behaviour
can be overwritten on a per device basis.

Signed-off-by: Boerge Struempfel <boerge.struempfel@gmail.com>
Link: https://lore.kernel.org/r/20230530141641.1155691-2-boerge.struempfel@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: add SPI_RX_CPHA_FLIP mode bit

Some SPI devices latch MOSI bits on one clock phase, but produce valid
MISO bits on the other phase. Add SPI_RX_CPHA_FLIP mode to instruct the
controller driver to flip CPHA for Rx (MISO) only transfers.

Signed-off-by: Baruch Siach <baruch.siach@siklu.com>
Link: https://lore.kernel.org/r/a715ca92713ca02071f33dcca9960a66a03c949a.1649702729.git.baruch@tkos.co.il
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: Add SPI_NO_TX/RX support

Transmit/receive only is a valid SPI mode. For example, the MOSI/TX line
might be missing from an ADC while for a DAC the MISO/RX line may be
optional. This patch adds these two new modes: SPI_NO_TX and
SPI_NO_RX. This way, the drivers will be able to identify if any of
these two lines is missing and to adjust the transfers accordingly.

Signed-off-by: Dragos Bogdan <dragos.bogdan@analog.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201221152936.53873-2-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>

spi: uapi: unify SPI modes into a single spi.h header

This change moves all the SPI mode bits into a separate 'spi.h' header in
uAPI. This is meant to re-use these definitions inside the kernel as well
as export them to userspace (via uAPI).

The SPI mode definitions have usually been duplicated between between
'include/linux/spi/spi.h' and 'include/uapi/linux/spi/spidev.h', so
whenever adding a new entry, this would need to be put in both headers.

They've been moved from 'include/linux/spi/spi.h', since that seems a bit
more complete; the bits have descriptions and there is the SPI_MODE_X_MASK.

This change also does a conversion of these bitfields to _BITUL() macro.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Link: https://lore.kernel.org/r/20201221152936.53873-1-alexandru.ardelean@analog.com
Signed-off-by: Mark Brown <broonie@kernel.org>