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>

diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
index a9983b6..002fb4d 100644 (file)
--- a/arch/arm/plat-omap/dma.c
+++ b/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);