spi/fsl-espi: avoid infinite loops on fsl_espi_cpu_irq()

It brought nearly infinite loops, and was possible to be
occurred only if the SPI transaction total size are not
alighed with 4. Loops are here at while (tmp--),
tmp is unsigned, and set it with minus value.

The loops are executed as a result of unexpected RX interrupt
occurrence after that. This interrupt may be hardware eratta
and is not fixed.

Fix mspi->len from minus value to 0 and print warning message.

Signed-off-by: Nobuteru Hayashi <hayashi.nbb@ncos.nec.co.jp>
Signed-off-by: Mark Brown <broonie@kernel.org>

1 files changed, 9 insertions, 1 deletions

diff --git a/drivers/spi/spi-fsl-espi.c b/drivers/spi/spi-fsl-espi.c
index 64d794b99803..8d85a3c343da 100644
--- a/drivers/spi/spi-fsl-espi.c
+++ b/drivers/spi/spi-fsl-espi.c
@@ -544,6 +544,7 @@ void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
         if (events & SPIE_NE) {
                 u32 rx_data, tmp;
                 u8 rx_data_8;
+                int rx_nr_bytes = 4;
                 int ret;
 
                 /* Spin until RX is done */
@@ -560,7 +561,14 @@ void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
 
                 if (mspi->len >= 4) {
                         rx_data = mpc8xxx_spi_read_reg(&reg_base->receive);
+                } else if (mspi->len <= 0) {
+                        dev_err(mspi->dev,
+                                "unexpected RX(SPIE_NE) interrupt occurred,\n"
+                                "(local rxlen %d bytes, reg rxlen %d bytes)\n",
+                                min(4, mspi->len), SPIE_RXCNT(events));
+                        rx_nr_bytes = 0;
                 } else {
+                        rx_nr_bytes = mspi->len;
                         tmp = mspi->len;
                         rx_data = 0;
                         while (tmp--) {
@@ -571,7 +579,7 @@ void fsl_espi_cpu_irq(struct mpc8xxx_spi *mspi, u32 events)
                         rx_data <<= (4 - mspi->len) * 8;
                 }
 
-                mspi->len -= 4;
+                mspi->len -= rx_nr_bytes;
 
                 if (mspi->rx)
                         mspi->get_rx(rx_data, mspi);