[PATCH 3/6] davinci: edma: clear events in edma_start()
stanley.miao
stanley.miao at windriver.com
Mon May 24 07:59:30 EDT 2010
This patch causes that the sound can not work normally on OMAP_L138.
Stanley.
Kevin Hilman wrote:
> 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);
>
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