drivers: spi: Add default char to mcux flexcomm spi driver
Adds optional device tree property to specify a default character
to clock out when the TX buffer pointer is NULL. If the property is
not set the existing behavior (default char of 0x00) is used.
I verified the expected behavior using an i.MX RT685 board and
logic analyzer that the def-char character is transmitted when
TX buffer pointer is NULL.
Signed-off-by: Bryce Wilkins <bryce.wilkins@gmail.com>
diff --git a/drivers/spi/spi_mcux_flexcomm.c b/drivers/spi/spi_mcux_flexcomm.c
index 1094a7a..f23feec 100644
--- a/drivers/spi/spi_mcux_flexcomm.c
+++ b/drivers/spi/spi_mcux_flexcomm.c
@@ -36,6 +36,7 @@
uint32_t post_delay;
uint32_t frame_delay;
uint32_t transfer_delay;
+ uint32_t def_char;
#ifdef CONFIG_PINCTRL
const struct pinctrl_dev_config *pincfg;
#endif
@@ -247,9 +248,10 @@
SPI_MasterInit(base, &master_config, clock_freq);
+ SPI_SetDummyData(base, (uint8_t)config->def_char);
+
SPI_MasterTransferCreateHandle(base, &data->handle,
spi_mcux_transfer_callback, data);
- SPI_SetDummyData(base, 0);
data->ctx.config = spi_cfg;
} else {
@@ -278,6 +280,8 @@
SPI_SlaveInit(base, &slave_config);
+ SPI_SetDummyData(base, (uint8_t)config->def_char);
+
SPI_SlaveTransferCreateHandle(base, &data->handle,
spi_mcux_transfer_callback, data);
}
@@ -823,6 +827,7 @@
.post_delay = DT_INST_PROP_OR(id, post_delay, 0), \
.frame_delay = DT_INST_PROP_OR(id, frame_delay, 0), \
.transfer_delay = DT_INST_PROP_OR(id, transfer_delay, 0), \
+ .def_char = DT_INST_PROP_OR(id, def_char, 0), \
SPI_MCUX_FLEXCOMM_PINCTRL_INIT(id) \
}; \
static struct spi_mcux_data spi_mcux_data_##id = { \
diff --git a/dts/bindings/spi/nxp,lpc-spi.yaml b/dts/bindings/spi/nxp,lpc-spi.yaml
index 7676179..02c7741 100644
--- a/dts/bindings/spi/nxp,lpc-spi.yaml
+++ b/dts/bindings/spi/nxp,lpc-spi.yaml
@@ -36,3 +36,10 @@
description: |
Delay in nanoseconds inserted between transfers when chip select is
deasserted. If not set, no additional delay is inserted.
+
+ def-char:
+ type: int
+ required: false
+ description: |
+ Default character clocked out when the TX buffer pointer is NULL.
+ Applies to SPI master and slave configurations.
