Re: [PATCH][OMAP3][sDMA] : Fixing the DMA chain transfer callback.

[Tony Lindgren <tony@atomide.com>]

Hi,

* Shilimkar, Santosh <santosh.shilimkar@ti.com> [081216 14:05]:
> Tony,
> Here is the patch for DMA to ease the chaining usage. OMAP mcbsp drivers makes use of this chaining feature but it's not pushed on mainline yet. It's available on zoom tree. Link for the same driver. http://git.omapzoom.org/?p=omapkernel.git;a=blob;f=arch/arm/mach-omap2/mcbsp.c;h=ce726c5d27eedb678ad3f981e2f5e08134e44e27;hb=2af15d1d7931a7c928d84057ed4494b77769de12

Hmm, the omap2_mcbsp_rx_dma_callback() and omap2_mcbsp_tx_dma_callback()
don't even use the lch parameter passed to them in the example above.

And can't you just use the data->chain_id to get the chain in the
callback function?

Tony



> 
> 
> From: Santosh Shilimkar <santosh.shilimkar@ti.com>
> 
> This patch reverts back the change done on OMAP dma library. It corrects the chaining callback and reduces the complexity for the DMA users in chaining. So with this patch, drivers making use of OMAP DMA chaining feature need not built any intelligence for chain related transfers in their callback using private data. 
> 
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
> Acked By : Nishant kamat <nskamat@ti.com>
> ---
> --- omapkernel.orig/arch/arm/plat-omap/dma.c	2008-12-04 11:11:07.000000000 +0530
> +++ omapkernel/arch/arm/plat-omap/dma.c	2008-12-16 16:59:42.066118383 +0530
> @@ -1936,7 +1936,11 @@ static int omap2_dma_handle_ch(int ch)
>  	}
>  
>  	if (likely(dma_chan[ch].callback != NULL))
> -		dma_chan[ch].callback(ch, status, dma_chan[ch].data);
> +		if (dma_chan[ch].chain_id != -1)
> +			dma_chan[ch].callback(dma_chan[ch].chain_id, status,
> +					      dma_chan[ch].data);
> +		else
> +			dma_chan[ch].callback(ch, status, dma_chan[ch].data);
>  
>  	dma_write(status, CSR(ch));