drivers: spi_mcux_lpspi: Clean up next_packet func

Next packet function is way more complicated than it needs to be. Clean
it up by simplifying the code and making readable helper functions.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>

Author: decsny

drivers/spi/spi_mcux_lpspi.c

@@ -125,53 +125,23 @@ static int spi_mcux_transfer_next_packet(const struct device *dev)
 	struct spi_mcux_data *data = dev->data;
 	LPSPI_Type *base = (LPSPI_Type *)DEVICE_MMIO_NAMED_GET(dev, reg_base);
 	struct spi_context *ctx = &data->ctx;
+	size_t max_chunk = spi_context_max_continuous_chunk(ctx);
 	lpspi_transfer_t transfer;
 	status_t status;
 
-	if ((ctx->tx_len == 0) && (ctx->rx_len == 0)) {
-		/* nothing left to rx or tx, we're done! */
-		spi_context_cs_control(&data->ctx, false);
-		spi_context_complete(&data->ctx, dev, 0);
+	if (max_chunk == 0) {
+		spi_context_cs_control(ctx, false);
+		spi_context_complete(ctx, dev, 0);
 		return 0;
 	}
 
+	data->transfer_len = max_chunk;
+
 	transfer.configFlags =
 		kLPSPI_MasterPcsContinuous | (ctx->config->slave << LPSPI_MASTER_PCS_SHIFT);
-
-	if (ctx->tx_len == 0) {
-		/* rx only, nothing to tx */
-		transfer.txData = NULL;
-		transfer.rxData = ctx->rx_buf;
-		transfer.dataSize = ctx->rx_len;
-	} else if (ctx->rx_len == 0) {
-		/* tx only, nothing to rx */
-		transfer.txData = (uint8_t *)ctx->tx_buf;
-		transfer.rxData = NULL;
-		transfer.dataSize = ctx->tx_len;
-	} else if (ctx->tx_len == ctx->rx_len) {
-		/* rx and tx are the same length */
-		transfer.txData = (uint8_t *)ctx->tx_buf;
-		transfer.rxData = ctx->rx_buf;
-		transfer.dataSize = ctx->tx_len;
-	} else if (ctx->tx_len > ctx->rx_len) {
-		/* Break up the tx into multiple transfers so we don't have to
-		 * rx into a longer intermediate buffer. Leave chip select
-		 * active between transfers.
-		 */
-		transfer.txData = (uint8_t *)ctx->tx_buf;
-		transfer.rxData = ctx->rx_buf;
-		transfer.dataSize = ctx->rx_len;
-	} else {
-		/* Break up the rx into multiple transfers so we don't have to
-		 * tx from a longer intermediate buffer. Leave chip select
-		 * active between transfers.
-		 */
-		transfer.txData = (uint8_t *)ctx->tx_buf;
-		transfer.rxData = ctx->rx_buf;
-		transfer.dataSize = ctx->tx_len;
-	}
-
-	data->transfer_len = transfer.dataSize;
+	transfer.txData = (ctx->tx_len == 0 ? NULL : ctx->tx_buf);
+	transfer.rxData = (ctx->rx_len == 0 ? NULL : ctx->rx_buf);
+	transfer.dataSize = max_chunk;
 
 	status = LPSPI_MasterTransferNonBlocking(base, &data->handle, &transfer);
 	if (status != kStatus_Success) {