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authorPeter Ujfalusi <peter.ujfalusi@ti.com>2011-12-09 13:38:00 -0800
committerTony Lindgren <tony@atomide.com>2011-12-09 13:38:00 -0800
commit7ba966804f58ccd81375827a71222efaa131aa70 (patch)
tree8d8b39fe1c77a937174b9d604f8cc554d18d4366 /arch/arm/plat-omap/dma.c
parent5611cc4572e889b62a7b4c72a413536bf6a9c416 (diff)
downloadop-kernel-dev-7ba966804f58ccd81375827a71222efaa131aa70.zip
op-kernel-dev-7ba966804f58ccd81375827a71222efaa131aa70.tar.gz
ARM: OMAP2+: DMA: Workaround for invalid source position
If the DMA source position has been asked before the first actual data transfer has been done, the CSAC register does not contain valid information. We can identify this situation by checking the CDAC register: CDAC != 0 indicates that the DMA transfer on the channel has been started already. When CDAC == 0 we can not trust the CSAC value since it has not been updated, and can contain random number. Return the start address in case the DMA has not jet started. Note: The CDAC register has been initialized to 0 at dma_start time. 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>
Diffstat (limited to 'arch/arm/plat-omap/dma.c')
-rw-r--r--arch/arm/plat-omap/dma.c12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
index c22217c..a9983b6 100644
--- a/arch/arm/plat-omap/dma.c
+++ b/arch/arm/plat-omap/dma.c
@@ -1034,6 +1034,18 @@ dma_addr_t omap_get_dma_src_pos(int lch)
if (IS_DMA_ERRATA(DMA_ERRATA_3_3) && offset == 0)
offset = p->dma_read(CSAC, lch);
+ if (!cpu_is_omap15xx()) {
+ /*
+ * CDAC == 0 indicates that the DMA transfer on the channel has
+ * not been started (no data has been transferred so far).
+ * Return the programmed source start address in this case.
+ */
+ if (likely(p->dma_read(CDAC, lch)))
+ offset = p->dma_read(CSAC, lch);
+ else
+ offset = p->dma_read(CSSA, lch);
+ }
+
if (cpu_class_is_omap1())
offset |= (p->dma_read(CSSA, lch) & 0xFFFF0000);
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