linux-kernel - Re: [PATCH v2] serial: pl011: Add Device Tree support to request DMA channels

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Message-ID: <20130418083922.GC3137@gmail.com>
Date:	Thu, 18 Apr 2013 09:39:22 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	arnd@...db.de, linus.walleij@...ricsson.com,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>
Subject: Re: [PATCH v2] serial: pl011: Add Device Tree support to request DMA
 channels

On Thu, 18 Apr 2013, Russell King - ARM Linux wrote:

> On Thu, Apr 18, 2013 at 09:14:16AM +0100, Lee Jones wrote:
> > @@ -269,7 +270,10 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
> >  	dma_cap_zero(mask);
> >  	dma_cap_set(DMA_SLAVE, mask);
> >  
> > -	chan = dma_request_channel(mask, plat->dma_filter, plat->dma_tx_param);
> > +	chan = dma_request_slave_channel_compat(mask,
> > +				(plat) ? plat->dma_filter : NULL,
> > +				(plat) ? plat->dma_tx_param : NULL,
> > +				uap->port.dev, "tx");
> >  	if (!chan) {
> >  		dev_err(uap->port.dev, "no TX DMA channel!\n");
> >  		return;
> 
> This suffers the same problem with your MMCI patch.  If you're using DT and
> don't provide the DMA information, you get errors printed.  That's not on
> for an optional driver feature, especially when that feature causes
> functional difficulties on various platforms and so is _purposely_ omitted.

How does that differ from using pdata and not passing DMA information?

-- 
Lee Jones
Linaro ST-Ericsson Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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