From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [Patch v3 2/2] dmaengine: qcom_bam_dma: Add device tree binding Date: Tue, 28 Jan 2014 13:05:10 +0100 Message-ID: <4916428.f0GtxdkWKj@wuerfel> References: <1390890471-14882-1-git-send-email-agross@codeaurora.org> <20140128111756.GE15937@n2100.arm.linux.org.uk> <20140128113242.GJ10628@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20140128113242.GJ10628@intel.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: Vinod Koul Cc: devicetree@vger.kernel.org, Lars-Peter Clausen , Russell King - ARM Linux , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Gross , dmaengine@vger.kernel.org, Dan Williams , linux-arm-kernel@lists.infradead.org List-Id: linux-arm-msm@vger.kernel.org On Tuesday 28 January 2014 17:02:42 Vinod Koul wrote: > On Tue, Jan 28, 2014 at 11:17:57AM +0000, Russell King - ARM Linux wrote: > > On Tue, Jan 28, 2014 at 10:16:53AM +0100, Arnd Bergmann wrote: > > > On Tuesday 28 January 2014 10:05:35 Lars-Peter Clausen wrote: > > > > Why does the direction needs to be specified in specifier? I see two > > > > options, either the direction per is fixed in hardware. In that case the DMA > > > > controller node should describe which channel is which direction. Or the > > > > direction is not fixed in hardware and can be changed at runtime in which > > > > case it should be set on a per descriptor basis. > > > > > > Normally the direction is implied by dmaengine_slave_config(). > > > > No. The direction argument in there is deprecated - we've been talking > > about removing it for some time. > > > > DMA engine drivers should store all parameters of the configuration, and > > then select the appropriate ones when preparing a transfer (which itself > > involves a direction.) > > Right all the prep_ calls for slave cases have explcit direction argument so > sending it using slave config makes no sense. So will remove it after the merge > window closes and fix Ok, thanks for clearing up my mistake. However, the argument remains: the direction doesn't need to be in the DT DMA descriptor since it gets set by software anyway. Arnd