davinci: edma: clear events in edma_start()

This patch fixes an issue where a DMA channel can erroneously process an
event generated by a previous transfer.  A failure case is where DMA is
being used for SPI transmit and receive channels on OMAP L138.  In this
case there is a single bit that controls all event generation from the
SPI peripheral.  Therefore it is possible that between when edma_stop()
has been called for the transmit channel on a previous transfer and
edma_start() is called for the transmit channel on a subsequent transfer,
that a transmit event has been generated.

The fix is to clear events in edma_start().  This prevents false events
from being processed when events are enabled for that channel.

Signed-off-by: Brian Niebuhr <bniebuhr@efjohnson.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>

diff --git a/arch/arm/mach-davinci/dma.c b/arch/arm/mach-davinci/dma.c
index 15dd886df04ca08cec53abb11ed9a6105a3a81c8..260485cc76dfcd8caa676f71ecd1895b4a4c1a69 100644 (file)
--- a/arch/arm/mach-davinci/dma.c
+++ b/arch/arm/mach-davinci/dma.c
@@ -1266,7 +1266,8 @@ int edma_start(unsigned channel)
                /* EDMA channel with event association */
                pr_debug("EDMA: ER%d %08x\n", j,
                        edma_shadow0_read_array(ctlr, SH_ER, j));
-               /* Clear any pending error */
+               /* Clear any pending event or error */
+               edma_write_array(ctlr, EDMA_ECR, j, mask);
                edma_write_array(ctlr, EDMA_EMCR, j, mask);
                /* Clear any SER */
                edma_shadow0_write_array(ctlr, SH_SECR, j, mask);