Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752466AbaATNf3 (ORCPT ); Mon, 20 Jan 2014 08:35:29 -0500 Received: from mail-lb0-f182.google.com ([209.85.217.182]:48708 "EHLO mail-lb0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbaATNf1 (ORCPT ); Mon, 20 Jan 2014 08:35:27 -0500 MIME-Version: 1.0 In-Reply-To: <201401201239.47665.arnd@arndb.de> References: <1389894803-4147-1-git-send-email-sthokal@xilinx.com> <201401171713.08550.arnd@arndb.de> <201401201239.47665.arnd@arndb.de> Date: Mon, 20 Jan 2014 19:05:25 +0530 X-Google-Sender-Auth: K5Kmd_av9gxyyBrQ6bzU0rRgw0I Message-ID: Subject: Re: [PATCH] dma: Add Xilinx AXI Video Direct Memory Access Engine driver support From: Srikanth Thokala To: Arnd Bergmann Cc: Srikanth Thokala , linux-arm-kernel@lists.infradead.org, dan.j.williams@intel.com, vinod.koul@intel.com, michal.simek@xilinx.com, Grant Likely , robh+dt@kernel.org, dmaengine@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Arnd, Sorry for the duplication. Ccing others. On Mon, Jan 20, 2014 at 5:09 PM, Arnd Bergmann wrote: > On Monday 20 January 2014, Srikanth Thokala wrote: >> On Fri, Jan 17, 2014 at 9:43 PM, Arnd Bergmann wrote: >> > On Thursday 16 January 2014, Srikanth Thokala wrote: >> > I also assume that some of the properties should just go away: >> > >> > * xlnx,device-id should be the argument in the handle from the slave device >> >> We can have multiple instances of this VDMA IP configured in the FPGA and we >> need a unique identifier for each VDMA device that is present in the FPGA. >> This device-id dt parameter forms the filter mask for the slave devices. As an >> example, this can be used to get a channel of specific VDMA device (assuming >> multiple instances) using the API dma_request_channel(). Please note this >> is an example of a slave device that doesnt have dt node. > > That is not a valid scenario: You should not try to support legacy > slave devices (without DT) connected to a dma-engine that is initialized > using DT. If you still in the progress of converting drivers to DT, you > can use auxdata to attach additional information that can be used for > those slave devices, but the code should be kept out of the mainline > kernel, and I don't want to see it manifest in the bindings. I see your point. Thank you for the clarification. I will fix this in my v2. > >> > * data width should be a property of the slave driver that is configured >> > through dma_slave_config(), unless you can have dma engines that only >> > support certain a width. >> >> Yes, this VDMA engine soft IP support only certain widths, which is >> configurable during IP synthesis. > > But what is this property used for in that case? Surely you can't > connect a slave device to a dmaengine if the bus width doesn't match. > You probably have a point here, but I don't understand it yet. There is a Data-Realignment Engine (DRE) in the IP which is only available for data width setting of 64-bits and less. So, we use the data-width DT parameter to verify this condition and we update alignment shift accordingly. Srikanth > > Arnd > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/