[PATCH 5.10 053/167] spi: mediatek: fix fifo rx mode

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

From: Peter Hess <peter.hess@xxxxxxxxxx>

[ Upstream commit 3a70dd2d050331ee4cf5ad9d5c0a32d83ead9a43 ]

In FIFO mode were two problems:
- RX mode was never handled and
- in this case the tx_buf pointer was NULL and caused an exception

fix this by handling RX mode in mtk_spi_fifo_transfer

Fixes: a568231f4632 ("spi: mediatek: Add spi bus for Mediatek MT8173")
Signed-off-by: Peter Hess <peter.hess@xxxxxxxxxx>
Signed-off-by: Frank Wunderlich <frank-w@xxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20210706121609.680534-1-linux@xxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/spi/spi-mt65xx.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-mt65xx.c b/drivers/spi/spi-mt65xx.c
index 5d643051bf3d..8f2d112f0b5d 100644
--- a/drivers/spi/spi-mt65xx.c
+++ b/drivers/spi/spi-mt65xx.c
@@ -434,13 +434,23 @@ static int mtk_spi_fifo_transfer(struct spi_master *master,
 	mtk_spi_setup_packet(master);
 
 	cnt = xfer->len / 4;
-	iowrite32_rep(mdata->base + SPI_TX_DATA_REG, xfer->tx_buf, cnt);
+	if (xfer->tx_buf)
+		iowrite32_rep(mdata->base + SPI_TX_DATA_REG, xfer->tx_buf, cnt);
+
+	if (xfer->rx_buf)
+		ioread32_rep(mdata->base + SPI_RX_DATA_REG, xfer->rx_buf, cnt);
 
 	remainder = xfer->len % 4;
 	if (remainder > 0) {
 		reg_val = 0;
-		memcpy(&reg_val, xfer->tx_buf + (cnt * 4), remainder);
-		writel(reg_val, mdata->base + SPI_TX_DATA_REG);
+		if (xfer->tx_buf) {
+			memcpy(&reg_val, xfer->tx_buf + (cnt * 4), remainder);
+			writel(reg_val, mdata->base + SPI_TX_DATA_REG);
+		}
+		if (xfer->rx_buf) {
+			reg_val = readl(mdata->base + SPI_RX_DATA_REG);
+			memcpy(xfer->rx_buf + (cnt * 4), &reg_val, remainder);
+		}
 	}
 
 	mtk_spi_enable_transfer(master);
-- 
2.30.2