spi: spi-fsl-dspi: XSPI FIFO handling (in TCFQ mode)

This implements handling of split CMD and TX FIFO queues for XSPI when
running in TCFQ mode.

It should be simple to add it to EOQ mode also.  Currently, EOQ mode is
only used with coldfire.  So if coldfire DSPI supports XSPI, XSPI FIFO
handling should be added to EOQ mode also.
Signed-off-by: Esben Haabendal <eha@deif.com>
Acked-by: Martin Hundebøll <martin@geanix.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-dspi.c

@@ -215,15 +215,17 @@ struct fsl_dspi {
 	struct fsl_dspi_dma	*dma;
 };
 
-static u16 dspi_pop_tx(struct fsl_dspi *dspi)
+static u32 dspi_pop_tx(struct fsl_dspi *dspi)
 {
-	u16 txdata = 0;
+	u32 txdata = 0;
 
 	if (dspi->tx) {
 		if (dspi->bytes_per_word == 1)
 			txdata = *(u8 *)dspi->tx;
-		else /* dspi->bytes_per_word == 2 */
+		else if (dspi->bytes_per_word == 2)
 			txdata = *(u16 *)dspi->tx;
+		else  /* dspi->bytes_per_word == 4 */
+			txdata = *(u32 *)dspi->tx;
 		dspi->tx += dspi->bytes_per_word;
 	}
 	dspi->len -= dspi->bytes_per_word;
@@ -249,8 +251,10 @@ static void dspi_push_rx(struct fsl_dspi *dspi, u32 rxdata)
 
 	if (dspi->bytes_per_word == 1)
 		*(u8 *)dspi->rx = rxdata;
-	else /* dspi->bytes_per_word == 2 */
+	else if (dspi->bytes_per_word == 2)
 		*(u16 *)dspi->rx = rxdata;
+	else /* dspi->bytes_per_word == 4 */
+		*(u32 *)dspi->rx = rxdata;
 	dspi->rx += dspi->bytes_per_word;
 }
 
@@ -564,12 +568,47 @@ static void fifo_write(struct fsl_dspi *dspi)
 	regmap_write(dspi->regmap, SPI_PUSHR, dspi_pop_tx_pushr(dspi));
 }
 
+static void cmd_fifo_write(struct fsl_dspi *dspi)
+{
+	u16 cmd = dspi->tx_cmd;
+
+	if (dspi->len > 0)
+		cmd |= SPI_PUSHR_CMD_CONT;
+	regmap_write(dspi->regmap_pushr, PUSHR_CMD, cmd);
+}
+
+static void tx_fifo_write(struct fsl_dspi *dspi, u16 txdata)
+{
+	regmap_write(dspi->regmap_pushr, PUSHR_TX, txdata);
+}
+
 static void dspi_tcfq_write(struct fsl_dspi *dspi)
 {
 	/* Clear transfer count */
 	dspi->tx_cmd |= SPI_PUSHR_CMD_CTCNT;
-	/* Write one entry to both TX FIFO and CMD FIFO simultaneously */
-	fifo_write(dspi);
+
+	if (dspi->devtype_data->xspi_mode && dspi->bits_per_word > 16) {
+		/* Write two TX FIFO entries first, and then the corresponding
+		 * CMD FIFO entry.
+		 */
+		u32 data = dspi_pop_tx(dspi);
+
+		if (dspi->cur_chip->ctar_val & SPI_CTAR_LSBFE(1)) {
+			/* LSB */
+			tx_fifo_write(dspi, data & 0xFFFF);
+			tx_fifo_write(dspi, data >> 16);
+		} else {
+			/* MSB */
+			tx_fifo_write(dspi, data >> 16);
+			tx_fifo_write(dspi, data & 0xFFFF);
+		}
+		cmd_fifo_write(dspi);
+	} else {
+		/* Write one entry to both TX FIFO and CMD FIFO
+		 * simultaneously.
+		 */
+		fifo_write(dspi);
+	}
 }
 
 static u32 fifo_read(struct fsl_dspi *dspi)
@@ -656,8 +695,10 @@ static int dspi_transfer_one_message(struct spi_master *master,
 		dspi->bits_per_word = transfer->bits_per_word;
 		if (transfer->bits_per_word <= 8)
 			dspi->bytes_per_word = 1;
-		else
+		else if (transfer->bits_per_word <= 16)
 			dspi->bytes_per_word = 2;
+		else
+			dspi->bytes_per_word = 4;
 
 		regmap_update_bits(dspi->regmap, SPI_MCR,
 				   SPI_MCR_CLR_TXF | SPI_MCR_CLR_RXF,