ARM: OMAP2+: DMA: Workaround for invalid destination position

If the DMA destination position has been asked before the
first actual data transfer has been done, the CDAC
register still contains 0 (it is initialized to 0 at
omsp_dma_start).
If CDAC == 0, return the programmed start address.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Reviewed-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/plat-omap/dma.c

@@ -1074,8 +1074,16 @@ dma_addr_t omap_get_dma_dst_pos(int lch)
 	 * omap 3.2/3.3 erratum: sometimes 0 is returned if CSAC/CDAC is
 	 * read before the DMA controller finished disabling the channel.
 	 */
-	if (!cpu_is_omap15xx() && offset == 0)
+	if (!cpu_is_omap15xx() && offset == 0) {
 		offset = p->dma_read(CDAC, lch);
+		/*
+		 * CDAC == 0 indicates that the DMA transfer on the channel has
+		 * not been started (no data has been transferred so far).
+		 * Return the programmed destination start address in this case.
+		 */
+		if (unlikely(!offset))
+			offset = p->dma_read(CDSA, lch);
+	}
 
 	if (cpu_class_is_omap1())
 		offset |= (p->dma_read(CDSA, lch) & 0xFFFF0000);