[PATCH 3/6] davinci: edma: clear events in edma_start()

[Kevin Hilman]

From: Brian Niebuhr <bniebuhr3 at gmail.com>

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 at efjohnson.com>
Signed-off-by: Kevin Hilman <khilman at deeprootsystems.com>
---
 arch/arm/mach-davinci/dma.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/arch/arm/mach-davinci/dma.c b/arch/arm/mach-davinci/dma.c
index 15dd886..260485c 100644
--- 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);
-- 
1.7.0.2