ARM: S3C64XX: DMA: Protect buffer pointers while manipulation

Ensure the DMA buffer points are not updated from
another source during the process of enquing a buffer.
Signed-off-by: NJassi Brar <jassi.brar@samsung.com>
[ben-linux@fluff.org: Updated patch comment]
Signed-off-by: NBen Dooks <ben-linux@fluff.org>

arch/arm/plat-s3c64xx/dma.c

@@ -339,6 +339,7 @@ int s3c2410_dma_enqueue(unsigned int channel, void *id,
 	struct s3c64xx_dma_buff *next;
 	struct s3c64xx_dma_buff *buff;
 	struct pl080s_lli *lli;
+	unsigned long flags;
 	int ret;
 
 	WARN_ON(!chan);
@@ -366,6 +367,8 @@ int s3c2410_dma_enqueue(unsigned int channel, void *id,
 
 	s3c64xx_dma_fill_lli(chan, lli, data, size);
 
+	local_irq_save(flags);
+
 	if ((next = chan->next) != NULL) {
 		struct s3c64xx_dma_buff *end = chan->end;
 		struct pl080s_lli *endlli = end->lli;
@@ -397,6 +400,8 @@ int s3c2410_dma_enqueue(unsigned int channel, void *id,
 		s3c64xx_lli_to_regs(chan, lli);
 	}
 
+	local_irq_restore(flags);
+
 	show_lli(lli);
 
 	dbg_showchan(chan);