linux-kernel - Re: [RFC PATCH 10/13] spi: omap2-mcspi: dma_request_slave

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Message-ID: <20120920220931.GJ28835@atomide.com>
Date:	Thu, 20 Sep 2012 15:09:31 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Matt Porter <mporter@...com>
Cc:	Sekhar Nori <nsekhar@...com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Benoit Cousson <b-cousson@...com>,
	Russell King <linux@....linux.org.uk>,
	Vinod Koul <vinod.koul@...el.com>,
	Rob Landley <rob@...dley.net>, Chris Ball <cjb@...top.org>,
	Devicetree Discuss <devicetree-discuss@...ts.ozlabs.org>,
	Linux OMAP List <linux-omap@...r.kernel.org>,
	Linux ARM Kernel List <linux-arm-kernel@...ts.infradead.org>,
	Linux DaVinci Kernel List 
	<davinci-linux-open-source@...ux.davincidsp.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Documentation List <linux-doc@...r.kernel.org>,
	Linux MMC List <linux-mmc@...r.kernel.org>,
	Linux SPI Devel List 
	<spi-devel-general@...ts.sourceforge.net>,
	Arnd Bergmann <arnd@...db.de>, Dan Williams <djbw@...com>,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [RFC PATCH 10/13] spi: omap2-mcspi:
 dma_request_slave_channel() support for DT platforms

* Matt Porter <mporter@...com> [120920 07:43]:
> For platforms with DT populated, use dma_request_slave_channel()
> to acquire the DMA channel. For !DT platforms, we fall back to
> explicitly passing the omap_dma_filter_fn() to dma_request_channel().
> Once all platforms boot from DT, the dma_request_channel() path can
> be dropped.
> 
> Signed-off-by: Matt Porter <mporter@...com>
> ---
>  drivers/spi/spi-omap2-mcspi.c |   68 +++++++++++++++++++++++++++++------------
>  1 file changed, 48 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
> index 9502566..1cf1072 100644
> --- a/drivers/spi/spi-omap2-mcspi.c
> +++ b/drivers/spi/spi-omap2-mcspi.c
> @@ -104,6 +104,9 @@ struct omap2_mcspi_dma {
>  
>  	struct completion dma_tx_completion;
>  	struct completion dma_rx_completion;
> +
> +	char dma_rx_ch_name[14];
> +	char dma_tx_ch_name[14];
>  };
>  
>  /* use PIO for small transfers, avoiding DMA setup/teardown overhead and
> @@ -798,14 +801,26 @@ static int omap2_mcspi_request_dma(struct spi_device *spi)
>  	dma_cap_zero(mask);
>  	dma_cap_set(DMA_SLAVE, mask);
>  	sig = mcspi_dma->dma_rx_sync_dev;
> -	mcspi_dma->dma_rx = dma_request_channel(mask, omap_dma_filter_fn, &sig);
> +	if (spi->dev.of_node)
> +		mcspi_dma->dma_rx =
> +			dma_request_slave_channel(&master->dev,
> +						  mcspi_dma->dma_rx_ch_name);
> +	else
> +		mcspi_dma->dma_rx =
> +			dma_request_channel(mask, omap_dma_filter_fn, &sig);
>  	if (!mcspi_dma->dma_rx) {
>  		dev_err(&spi->dev, "no RX DMA engine channel for McSPI\n");
>  		return -EAGAIN;
>  	}
>  

Hmm this does not look nice.. We should be able to somehow not to care about
the configuration at the mcspi driver level.

Regards,

Tony
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