[MTD] [NAND] Blackfin NFC Driver: do not clobber DMAC1_PERIMUX

Only set DMAC1_PERIMUX once we have requested and been granted the dma
channel to prevent breaking other peripherals in the error case

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/nand/bf5xx_nand.c

@@ -552,28 +552,26 @@ static void bf5xx_nand_dma_write_buf(struct mtd_info *mtd,
 static int bf5xx_nand_dma_init(struct bf5xx_nand_info *info)
 {
 	int ret;
-	unsigned short val;
 
 	/* Do not use dma */
 	if (!hardware_ecc)
 		return 0;
 
 	init_completion(&info->dma_completion);
 
-#ifdef CONFIG_BF54x
-	/* Setup DMAC1 channel mux for NFC which shared with SDH */
-	val = bfin_read_DMAC1_PERIMUX();
-	val &= 0xFFFE;
-	bfin_write_DMAC1_PERIMUX(val);
-	SSYNC();
-#endif
 	/* Request NFC DMA channel */
 	ret = request_dma(CH_NFC, "BF5XX NFC driver");
 	if (ret < 0) {
 		dev_err(info->device, " unable to get DMA channel\n");
 		return ret;
 	}
 
+#ifdef CONFIG_BF54x
+	/* Setup DMAC1 channel mux for NFC which shared with SDH */
+	bfin_write_DMAC1_PERIMUX(bfin_read_DMAC1_PERIMUX() & ~1);
+	SSYNC();
+#endif
+
 	set_dma_callback(CH_NFC, (void *) bf5xx_nand_dma_irq, (void *) info);
 
 	/* Turn off the DMA channel first */