dts: bindings: spi: add support to set CPOL, CPHA, and HOLD_CS in dts file

Add support to set SPI clock polarity (CPOL), clock phase (CPHA), and
hold-on-cs in a dts file to get rid of using related macros in spi.c driver
since each board may work on a different SPI mode rather than the default
one (based on CPOL and CPHA).

Signed-off-by: Ali Hozhabri <ali.hozhabri@st.com>
This commit is contained in:
Ali Hozhabri 2023-10-25 11:02:20 +02:00 committed by Martí Bolívar
commit eb2f5ceb19

View file

@ -40,3 +40,21 @@ properties:
enum:
- 0
- 32768
spi-cpol:
type: boolean
description: |
SPI clock polarity which indicates the clock idle state.
If it is used, the clock idle state is logic high; otherwise, low.
spi-cpha:
type: boolean
description: |
SPI clock phase that indicates on which edge data is sampled.
If it is used, data is sampled on the second edge; otherwise, on the first edge.
spi-hold-cs:
type: boolean
description: |
In some cases, it is necessary for the master to manage SPI chip select
under software control, so that multiple spi transactions can be performed
without releasing it. A typical use case is variable length SPI packets
where the first spi transaction reads the length and the second spi transaction
reads length bytes.