[PATCH v1] spi: dw: add check for Rx FIFO overflow

[Maksim Kiselev]

If even one byte is lost due to Rx FIFO overflow then we will never
exit the read loop. Because the (priv->rx != priv->rx_end) condition will
be always true.

Let's check if Rx FIFO overflow occurred and exit the read loop
in this case.

Signed-off-by: Maksim Kiselev <biguncle...@gmail.com>
---
 drivers/spi/designware_spi.c | 24 +++++++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/designware_spi.c b/drivers/spi/designware_spi.c
index 1c7d0ca310..0f443bff8e 100644
--- a/drivers/spi/designware_spi.c
+++ b/drivers/spi/designware_spi.c
@@ -111,6 +111,15 @@
 #define SR_TX_ERR                      BIT(5)
 #define SR_DCOL                                BIT(6)
 
+/* Bit fields in ISR, IMR, RISR, 7 bits */
+#define DW_SPI_INT_MASK                        GENMASK(5, 0)
+#define DW_SPI_INT_TXEI                        BIT(0)
+#define DW_SPI_INT_TXOI                        BIT(1)
+#define DW_SPI_INT_RXUI                        BIT(2)
+#define DW_SPI_INT_RXOI                        BIT(3)
+#define DW_SPI_INT_RXFI                        BIT(4)
+#define DW_SPI_INT_MSTI                        BIT(5)
+
 #define RX_TIMEOUT                     1000            /* timeout in ms */
 
 struct dw_spi_plat {
@@ -588,7 +597,7 @@ static int dw_spi_exec_op(struct spi_slave *slave, const 
struct spi_mem_op *op)
        struct dw_spi_priv *priv = dev_get_priv(bus);
        u8 op_len = op->cmd.nbytes + op->addr.nbytes + op->dummy.nbytes;
        u8 op_buf[op_len];
-       u32 cr0;
+       u32 cr0, sts;
 
        if (read)
                priv->tmode = CTRLR0_TMOD_EPROMREAD;
@@ -632,12 +641,21 @@ static int dw_spi_exec_op(struct spi_slave *slave, const 
struct spi_mem_op *op)
         * them to fail because we are not reading/writing the fifo fast enough.
         */
        if (read) {
-               priv->rx = op->data.buf.in;
+               void *prev_rx = priv->rx = op->data.buf.in;
                priv->rx_end = priv->rx + op->data.nbytes;
 
                dw_write(priv, DW_SPI_SER, 1 << spi_chip_select(slave->dev));
-               while (priv->rx != priv->rx_end)
+               while (priv->rx != priv->rx_end) {
                        dw_reader(priv);
+                       if (prev_rx == priv->rx) {
+                               sts = dw_read(priv, DW_SPI_RISR);
+                               if (sts & DW_SPI_INT_RXOI) {
+                                       dev_err(bus, "FIFO overflow on Rx\n");
+                                       return -EIO;
+                               }
+                       }
+                       prev_rx = priv->rx;
+               }
        } else {
                u32 val;
 
-- 
2.40.1