linux-kernel - Re: [PATCH v2 3/7] dmaengine: Add driver for TI DMA crossbar on DRA7x

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Date:	Thu, 26 Mar 2015 08:22:04 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	Vinod Koul <vinod.koul@...el.com>, linux@....linux.org.uk,
	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 v2 3/7] dmaengine: Add driver for TI DMA crossbar on DRA7x

* Peter Ujfalusi <peter.ujfalusi@...com> [150326 05:32]:
> On 03/26/2015 12:56 PM, Vinod Koul wrote:
> >> +
> >> +static void ti_dma_xbar_free(struct device *dev, void *route_data)
> >> +{
> >> +	struct ti_dma_xbar_data *xbar = dev_get_drvdata(dev);
> >> +	struct ti_dma_xbar_map *map = route_data;
> >> +
> >> +	dev_dbg(dev, "Unmapping XBAR%d (was routed to %d)\n",
> >> +		map->xbar_in, map->xbar_out);
> >> +
> >> +	regmap_write(xbar->regmap, map->xbar_out * 2, 0);
> > just out of curiosity how much do you save using regmap :)
> 
> good point, not much I guess. I had it implemented w/o regmap as well, but
> thought why not use regmap if it is available.

Regmap is nice for slow devices and devices in a shared register
range like the omap syscon general area. For normal use, there's
quite a bit of overhead with regmap compared to just read/write :)

Regards,

Tony
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