Blackfin: add SSYNC to set_dma_sg() for descriptor fetching

Make sure the internal core buffers are flushed before telling the DMA
engine to fetch the descriptor structure so that it gets the right values.

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/include/asm/dma.h

@@ -206,10 +206,16 @@ static inline unsigned long get_dma_curr_addr(unsigned int channel)
 
 static inline void set_dma_sg(unsigned int channel, struct dmasg *sg, int ndsize)
 {
+	/* Make sure the internal data buffers in the core are drained
+	 * so that the DMA descriptors are completely written when the
+	 * DMA engine goes to fetch them below.
+	 */
+	SSYNC();
+
+	dma_ch[channel].regs->next_desc_ptr = sg;
 	dma_ch[channel].regs->cfg =
 		(dma_ch[channel].regs->cfg & ~(0xf << 8)) |
 		((ndsize & 0xf) << 8);
-	dma_ch[channel].regs->next_desc_ptr = sg;
 }
 
 static inline int dma_channel_active(unsigned int channel)