spi_mcux_lpspi: More precise configuration checks

These changes:
* Fix the check of the word size to be more useful
  - check min frame size instead of max
  - check for min word size requirement
  - add a clarifying comment about what the word size represents in
    hardware since the nomenclature from zephyr does not match the nxp
    references
* Add a clarifying comment about half duplex being supported by hardware
* Add LPSPI_ namespace to defines
* Change chip select error message to be more clear about the problem
* Move the check of the clock device being ready to the lpspi init,
  instead of checking it every time on configure. It probably also makes
  more sense to not ready the lpspi device if the clock is not ready.
* Move the bare-metal configuration of bit fields AFTER the SDK Init
  call.
* Return the proper error code if clock control call errors.

Signed-off-by: Declan Snyder <[email protected]>

Author: Declan Snyder

drivers/spi/spi_mcux_lpspi.c

@@ -29,8 +29,8 @@ LOG_MODULE_REGISTER(spi_mcux_lpspi, CONFIG_SPI_LOG_LEVEL);
 /* If any hardware revisions change this, make it into a DT property.
  * DONT'T make #ifdefs here by platform.
  */
-#define CHIP_SELECT_COUNT 4
-#define MAX_DATA_WIDTH    4096
+#define LPSPI_CHIP_SELECT_COUNT   4
+#define LPSPI_MIN_FRAME_SIZE_BITS 8
 
 /* Required by DEVICE_MMIO_NAMED_* macros */
 #define DEV_CFG(_dev)  ((const struct spi_mcux_config *)(_dev)->config)
@@ -161,29 +161,35 @@ static int spi_mcux_configure(const struct device *dev, const struct spi_config
 	uint32_t word_size = SPI_WORD_SIZE_GET(spi_cfg->operation);
 	lpspi_master_config_t master_config;
 	uint32_t clock_freq;
+	int ret;
 
 	if (spi_cfg->operation & SPI_HALF_DUPLEX) {
+		/* the IP DOES support half duplex, need to implement driver support */
 		LOG_ERR("Half-duplex not supported");
 		return -ENOTSUP;
 	}
 
-	if (spi_cfg->slave > CHIP_SELECT_COUNT) {
-		LOG_ERR("Slave %d is greater than %d", spi_cfg->slave, CHIP_SELECT_COUNT);
+	if (word_size < 8 || (word_size % 32 == 1)) {
+		/* Zephyr word size == hardware FRAME size (not word size)
+		 * Max frame size: 4096 bits
+		 *   (zephyr field is 6 bit wide for max 64 bit size, no need to check)
+		 * Min frame size: 8 bits.
+		 * Minimum hardware word size is 2. Since this driver is intended to work
+		 * for 32 bit platforms, and 64 bits is max size, then only 33 and 1 are invalid.
+		 */
+		LOG_ERR("Word size %d not allowed", word_size);
 		return -EINVAL;
 	}
 
-	if (word_size > MAX_DATA_WIDTH) {
-		LOG_ERR("Word size %d is greater than %d", word_size, MAX_DATA_WIDTH);
+	if (spi_cfg->slave > LPSPI_CHIP_SELECT_COUNT) {
+		LOG_ERR("Peripheral %d select exceeds max %d", spi_cfg->slave,
+			LPSPI_CHIP_SELECT_COUNT - 1);
 		return -EINVAL;
 	}
 
-	if (!device_is_ready(config->clock_dev)) {
-		LOG_ERR("clock control device not ready");
-		return -ENODEV;
-	}
-
-	if (clock_control_get_rate(config->clock_dev, config->clock_subsys, &clock_freq)) {
-		return -EINVAL;
+	ret = clock_control_get_rate(config->clock_dev, config->clock_subsys, &clock_freq);
+	if (ret) {
+		return ret;
 	}
 
 	if (data->ctx.config != NULL) {
@@ -200,10 +206,6 @@ static int spi_mcux_configure(const struct device *dev, const struct spi_config
 		}
 	}
 
-	if (IS_ENABLED(CONFIG_DEBUG)) {
-		base->CR |= LPSPI_CR_DBGEN_MASK;
-	}
-
 	data->ctx.config = spi_cfg;
 
 	LPSPI_MasterGetDefaultConfig(&master_config);
@@ -227,6 +229,10 @@ static int spi_mcux_configure(const struct device *dev, const struct spi_config
 	LPSPI_MasterTransferCreateHandle(base, &data->handle, spi_mcux_master_callback, data);
 	LPSPI_SetDummyData(base, 0);
 
+	if (IS_ENABLED(CONFIG_DEBUG)) {
+		base->CR |= LPSPI_CR_DBGEN_MASK;
+	}
+
 	return 0;
 }
 
@@ -751,6 +757,11 @@ static int spi_mcux_init(const struct device *dev)
 
 	data->dev = dev;
 
+	if (!device_is_ready(config->clock_dev)) {
+		LOG_ERR("clock control device not ready");
+		return -ENODEV;
+	}
+
 	if (IS_ENABLED(CONFIG_SPI_MCUX_LPSPI_DMA) && lpspi_inst_has_dma(data)) {
 		err = lpspi_dma_devs_ready(data);
 	}