spi/omap_mcspi: catch xfers of non-multiple SPI word size

If an SPI access was not a multiple of the SPI word size,
the while() loop would spin and the rx/tx ptrs would be incremented
indefinitely.

Signed-off-by: Michael Jones <michael.jones@matrix-vision.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/omap2_mcspi.c

@@ -487,6 +487,9 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 	rx_reg		= base + OMAP2_MCSPI_RX0;
 	chstat_reg	= base + OMAP2_MCSPI_CHSTAT0;
 
+	if (c < (word_len>>3))
+		return 0;
+
 	if (word_len <= 8) {
 		u8		*rx;
 		const u8	*tx;
@@ -534,7 +537,7 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 				dev_vdbg(&spi->dev, "read-%d %02x\n",
 						word_len, *(rx - 1));
 			}
-		} while (c);
+		} while (c > (word_len>>3));
 	} else if (word_len <= 16) {
 		u16		*rx;
 		const u16	*tx;
@@ -581,7 +584,7 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 				dev_vdbg(&spi->dev, "read-%d %04x\n",
 						word_len, *(rx - 1));
 			}
-		} while (c);
+		} while (c > (word_len>>3));
 	} else if (word_len <= 32) {
 		u32		*rx;
 		const u32	*tx;
@@ -628,7 +631,7 @@ omap2_mcspi_txrx_pio(struct spi_device *spi, struct spi_transfer *xfer)
 				dev_vdbg(&spi->dev, "read-%d %08x\n",
 						word_len, *(rx - 1));
 			}
-		} while (c);
+		} while (c > (word_len>>3));
 	}
 
 	/* for TX_ONLY mode, be sure all words have shifted out */