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davinci: edma: clear events in edma_start()

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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>
This commit is contained in:
Brian Niebuhr 2010-03-09 16:48:03 -06:00 committed by Kevin Hilman
parent 5eb2e891f0
commit bb17ef102b
1 changed files with 2 additions and 1 deletions
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3
arch/arm/mach-davinci/dma.c
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@ -1266,7 +1266,8 @@ int edma_start(unsigned channel)
/* EDMA channel with event association */ /* EDMA channel with event association */
pr_debug("EDMA: ER%d %08x\n", j, pr_debug("EDMA: ER%d %08x\n", j,
edma_shadow0_read_array(ctlr, SH_ER, 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); edma_write_array(ctlr, EDMA_EMCR, j, mask);
/* Clear any SER */ /* Clear any SER */
edma_shadow0_write_array(ctlr, SH_SECR, j, mask); edma_shadow0_write_array(ctlr, SH_SECR, j, mask);