spi: Adding a new configuration bit for the frame format

So TI will no longer be the only frame format available, though it will
still be the default one. It will be possible to select the Motorola
frame format when relevant.

Signed-off-by: Tomasz Bursztyka <[email protected]>

Author: Tomasz Bursztyka

include/drivers/spi.h

@@ -117,6 +117,22 @@ extern "C" {
 #define SPI_CS_ACTIVE_HIGH	BIT(14)
 /** @} */
 
+/**
+ * @name SPI Frame Format
+ * @{
+ *
+ * 2 frame formats are exposed: Motorola and TI.
+ * The main difference is the behavior of the CS line. In Motorala it stays
+ * active the whole transfer. In TI, it's active only one serial clock period
+ * prior to actually make the transfer, it is thus inactive during the transfer,
+ * which ends when the clocks ends as well.
+ * By default, as it is the most commonly used, the Motorola frame format
+ * will prevail.
+ */
+#define SPI_FRAME_FORMAT_MOTOROLA	(0U << 15)
+#define SPI_FRAME_FORMAT_TI		(1U << 15)
+/** @} */
+
 /**
  * @name SPI MISO lines (if @kconfig{CONFIG_SPI_EXTENDED_MODES} is enabled)
  * @{
@@ -248,7 +264,7 @@ struct spi_cs_control {
  *     cs_hold             [ 12 ]      - Hold on the CS line if possible.
  *     lock_on             [ 13 ]      - Keep resource locked for the caller.
  *     cs_active_high      [ 14 ]      - Active high CS logic.
- *     reserved            [ 15 ]      - reserved for future use.
+ *     format              [ 15 ]      - Motorola or TI frame format (optional).
  * if @kconfig{CONFIG_SPI_EXTENDED_MODES} is defined:
  *     lines               [ 16 : 17 ] - MISO lines: Single/Dual/Quad/Octal.
  *     reserved            [ 18 : 31 ] - reserved for future use.