spi: s3c64xx: Use DMA mode from fifo size

[ Upstream commit a3d3eab ]

If the SPI data size is smaller than FIFO, it operates in PIO mode,
and if it is larger than FIFO size, it oerates in DMA mode.

If the SPI data size is equal to fifo, it operates in PIO mode and it is
separated to 2 transfers. To prevent it, it must operate in DMA mode
from the case where the data size and the fifo size are the same.

Fixes: 1ee8067 ("spi: s3c64xx: support interrupt based pio mode")
Signed-off-by: Jaewon Kim <jaewon02.kim@samsung.com>
Reviewed-by: Sam Protsenko <semen.protsenko@linaro.org>
Link: https://lore.kernel.org/r/20240329085840.65856-1-jaewon02.kim@samsung.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/spi/spi-s3c64xx.c

@@ -424,7 +424,7 @@ static bool s3c64xx_spi_can_dma(struct spi_controller *host,
 	struct s3c64xx_spi_driver_data *sdd = spi_controller_get_devdata(host);
 
 	if (sdd->rx_dma.ch && sdd->tx_dma.ch)
-		return xfer->len > sdd->fifo_depth;
+		return xfer->len >= sdd->fifo_depth;
 
 	return false;
 }
@@ -783,10 +783,9 @@ static int s3c64xx_spi_transfer_one(struct spi_controller *host,
 			return status;
 	}
 
-	if (!is_polling(sdd) && (xfer->len > fifo_len) &&
+	if (!is_polling(sdd) && xfer->len >= fifo_len &&
 	    sdd->rx_dma.ch && sdd->tx_dma.ch) {
 		use_dma = 1;
-
 	} else if (xfer->len >= fifo_len) {
 		tx_buf = xfer->tx_buf;
 		rx_buf = xfer->rx_buf;