From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Porter Subject: Re: [RFC PATCH 10/13] spi: omap2-mcspi: dma_request_slave_channel() support for DT platforms Date: Fri, 21 Sep 2012 14:37:29 -0400 Message-ID: <20120921183729.GI16522@beef> References: <1348152226-13588-1-git-send-email-mporter@ti.com> <1348152226-13588-11-git-send-email-mporter@ti.com> <20120920220931.GJ28835@atomide.com> <201209210816.01473.arnd@arndb.de> <20120921154247.GZ28835@atomide.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Linux DaVinci Kernel List , Chris Ball , Russell King , Linux Documentation List , Vinod Koul , Devicetree Discuss , Mark Brown , Linux MMC List , Linux Kernel Mailing List , Rob Herring , Dan Williams , Linux SPI Devel List , Linux OMAP List , Linux ARM Kernel List To: Tony Lindgren Return-path: Content-Disposition: inline In-Reply-To: <20120921154247.GZ28835-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: devicetree-discuss-bounces+gldd-devicetree-discuss=m.gmane.org-uLR06cmDAlY/bJ5BZ2RsiQ@public.gmane.org Sender: "devicetree-discuss" List-Id: linux-spi.vger.kernel.org On Fri, Sep 21, 2012 at 08:42:47AM -0700, Tony Lindgren wrote: > * Arnd Bergmann [120921 02:19]: > > On Thursday 20 September 2012, Tony Lindgren wrote: > > > > /* 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. > > > > I agree, but as far as I understand Vinod's plans, we would actually move > > all drivers over to dma_request_slave_channel() when we have an interface > > to register the lookup tables from platform code. > > > > I think the above is ok for a transitional phase and we can remove the > > fallback path when we have converted all platforms using this driver > > to either use DT or move to the new style way of passing the channel > > configuration. > > Can't we come up with a version of dma_request_slave_channel that works > both ways for now: > > mcspi_dma->dma_rx = > dma_request_slave_channel_compat(mask, omap_dma_filter_fn, &sig, > &master->dev, mcspi_dma->dma_rx_ch_name); > ... > > Then it's just question of patching away two lines later on rather than > having to add all this if else to all the drivers first, then patching > it away again. I think that something like that is workable with the implementation simply checking for of_node to do the right thing. -Matt