spi/bfin_spi: handle error/status changes after data interrupts

The error interrupt on the BF537 SIC cannot be enabled on a
per-peripheral basis.  Once the error interrupt is enabled
for one peripheral, it is automatically enabled for all.

So in the Blackfin on-chip SPI driver, we need to clear out
these known errors in the data interrupt once we've successfully
finished processing all of the pending data.
Signed-off-by: Michael Hennerich <michael.hennerich@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi_bfin5xx.c

@@ -504,6 +504,15 @@ static irqreturn_t bfin_spi_dma_irq_handler(int irq, void *dev_id)
 		"in dma_irq_handler dmastat:0x%x spistat:0x%x\n",
 		dmastat, spistat);
 
+	if (drv_data->rx != NULL) {
+		u16 cr = read_CTRL(drv_data);
+		/* discard old RX data and clear RXS */
+		bfin_spi_dummy_read(drv_data);
+		write_CTRL(drv_data, cr & ~BIT_CTL_ENABLE); /* Disable SPI */
+		write_CTRL(drv_data, cr & ~BIT_CTL_TIMOD); /* Restore State */
+		write_STAT(drv_data, BIT_STAT_CLR); /* Clear Status */
+	}
+
 	clear_dma_irqstat(drv_data->dma_channel);
 
 	/*