bluetooth: hci: spi: configurable CS delay

Make the common SPI CS delay property configurable from devicetree. This
can be required for using a nRF54L as a Bluetooth controller, since it
has an additional delay after waking up from the CS assertion until it
is ready to accept and transmit data (see OPS t_START_HFINT).

Signed-off-by: Jordan Yates <[email protected]>

Author: JordanYates

drivers/bluetooth/hci/spi.c

@@ -86,7 +86,8 @@ static K_KERNEL_STACK_DEFINE(spi_rx_stack, CONFIG_BT_DRV_RX_STACK_SIZE);
 static struct k_thread spi_rx_thread_data;
 
 static const struct spi_dt_spec bus = SPI_DT_SPEC_INST_GET(
-	0, SPI_OP_MODE_MASTER | SPI_TRANSFER_MSB | SPI_WORD_SET(8), 0);
+	0, SPI_OP_MODE_MASTER | SPI_TRANSFER_MSB | SPI_WORD_SET(8),
+	DT_INST_PROP(0, controller_cs_delay_us));
 
 static struct spi_buf spi_tx_buf;
 static struct spi_buf spi_rx_buf;

dts/bindings/bluetooth/zephyr,bt-hci-spi.yaml

@@ -24,6 +24,13 @@ properties:
       Minimum duration to hold the reset-gpios pin low for.
       If not specified no delay beyond the code path execution time is guaranteed.
 
+  controller-cs-delay-us:
+    type: int
+    default: 0
+    description:
+      Delay in microseconds to wait after asserting the CS line before starting the
+      transmission and before releasing the CS line after the transmission.
+
   controller-data-delay-us:
     type: int
     default: 20