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

From: [email-masked] (stanley.miao)
Date: Mon, 24 May 2010 19:59:30 +0800

This patch causes that the sound can not work normally on OMAP_L138.

Stanley.

Kevin Hilman wrote:
> From: Brian Niebuhr <[email-masked]>
>
> 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 <[email-masked]>
> Signed-off-by: Kevin Hilman <[email-masked]>
> ---
>  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);
>