spi_nxp_lpspi: Fix S32 regressions

There are two bugs that caused regression for S32:

First there is a silicon errata specifically for the mask version on
this board that causes FIFO flush to not work as expected. The
workaround is to do a module reset before each transfer.

Second there was a division error for word size > 1 byte. The division
should be rounded up, not down, otherwise there will be an infinite
interrupt loop because the TX fifo will not be written to but the TDR
interrupt enabled causes interrupt when TX fifo is empty.

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

Author: decsny

drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi.c

@@ -62,7 +62,7 @@ static inline size_t lpspi_rx_buf_write_words(const struct device *dev, uint8_t
 	struct spi_mcux_data *data = dev->data;
 	struct lpspi_driver_data *lpspi_data = (struct lpspi_driver_data *)data->driver_data;
 	struct spi_context *ctx = &data->ctx;
-	size_t buf_len = ctx->rx_len / lpspi_data->word_size_bytes;
+	size_t buf_len = DIV_ROUND_UP(ctx->rx_len, lpspi_data->word_size_bytes);
 	uint8_t words_read = 0;
 	size_t offset = 0;
 
@@ -158,7 +158,7 @@ static void lpspi_next_tx_fill(const struct device *dev)
 	size_t max_chunk;
 
 	/* Convert bytes to words for this xfer */
-	max_chunk = ctx->tx_len / lpspi_data->word_size_bytes;
+	max_chunk = DIV_ROUND_UP(ctx->tx_len, lpspi_data->word_size_bytes);
 	max_chunk = MIN(max_chunk, config->tx_fifo_size);
 	lpspi_data->fill_len = max_chunk;
 

drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi_common.c

@@ -57,6 +57,10 @@ int spi_mcux_configure(const struct device *dev, const struct spi_config *spi_cf
 		return ret;
 	}
 
+	base->CR |= LPSPI_CR_RST_MASK;
+	base->CR |= LPSPI_CR_RRF_MASK | LPSPI_CR_RTF_MASK;
+	base->CR = 0x00U;
+
 	if (data->ctx.config != NULL) {
 		/* Setting the baud rate in LPSPI_MasterInit requires module to be disabled. Only
 		 * disable if already configured, otherwise the clock is not enabled and the