From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from wx-out-0506.google.com (wx-out-0506.google.com [66.249.82.237]) by ozlabs.org (Postfix) with ESMTP id 8E1A4DDDF8 for ; Mon, 10 Sep 2007 08:10:13 +1000 (EST) Received: by wx-out-0506.google.com with SMTP id h27so837748wxd for ; Sun, 09 Sep 2007 15:10:12 -0700 (PDT) Message-ID: Date: Sun, 9 Sep 2007 15:10:12 -0700 From: "Dan Williams" Sender: dan.j.williams@gmail.com To: "Timur Tabi" Subject: Re: [PATCH 5/5] Add DMA engine driver for Freescale MPC85xx processors. In-Reply-To: <46E46A3F.2050708@freescale.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <11891624582950-git-send-email-wei.zhang@freescale.com> <46E46A3F.2050708@freescale.com> Cc: linuxppc-dev@ozlabs.org, shannon.nelson@intel.com, paulus@samba.org, linux-kernel@vger.kernel.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 9/9/07, Timur Tabi wrote: > Dan Williams wrote: > > > This routine implies that there is a piece of code somewhere that > > wants to select which channels it can use. A similar effect can be > > achieved by registering a dma_client with the dmaengine interface > > ('dma_async_client_register'). Then when the client code makes a call > > to 'dma_async_client_chan_request' it receives a 'dma_event_callback' > > for each channel in the system. It will also be asynchronously > > notified of channels entering and leaving the system. The goal is to > > share a common infrastructure for channel management. > > Are you familiar with the "flat device tree" used for PowerPC systems? The > "piece of code somewhere" is the device tree subsystem that parses the device > tree, which is compiled from the .dts files in arch/powerpc/boot/dts. > > The FDT is how PowerPC systems specify hardware configuration. In the case of > 85xx, the FDT contains entries for each DMA device (typically 2), and the > entries contain sub-entries for each DMA channel as well as the address of the > register sets for each channel. > Ahh, ok then this code is replacing what would normally be handled by the PCI bus enumeration code, or the platform device registrations for iop-adma in arch/arm/mach-iop13xx. Sorry for the noise with this comment. > -- > Timur Tabi > Linux Kernel Developer @ Freescale > - Thanks, Dan