linux-kernel - Re: [PATCH v3 6/7] dmaengine: omap-dma: Remove mapping between virtual channels and requests

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Date:	Fri, 27 Mar 2015 20:22:30 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	vinod.koul@...el.com, tony@...mide.com, grant.likely@...aro.org,
	dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, robh+dt@...nel.org, nm@...com
Subject: Re: [PATCH v3 6/7] dmaengine: omap-dma: Remove mapping between
 virtual channels and requests

On Fri, Mar 27, 2015 at 02:26:52PM +0200, Peter Ujfalusi wrote:
> Do not direct map the virtual channels to sDMA request number. When the
> sDMA is behind of a crossbar this direct mapping can cause situations when
> certain channel can not be requested since the crossbar request number
> will no longer match with the sDMA request line.
> The direct mapping for virtual channels with HW request lines will make it
> harder to implement MEM_TO_MEM mode for the driver.

There's no point having 127 virtual DMA channels then... is there?
We might as well reduce the number down to a more reasonable set
rather than wasting memory.

> @@ -1049,7 +1050,6 @@ static int omap_dma_chan_init(struct omap_dmadev *od, int dma_sig)
>  		return -ENOMEM;
>  
>  	c->reg_map = od->reg_map;
> -	c->dma_sig = dma_sig;

That's the only user of dma_sig in this function.  Why not remove it from
the function prototype and its caller?

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