From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: [PATCH 4/6] DMA: PL330: Add device tree support Date: Fri, 26 Aug 2011 15:23:05 +0100 Message-ID: <20110826142305.GA23469@n2100.arm.linux.org.uk> References: <1314348014-2481-1-git-send-email-thomas.abraham@linaro.org> <1314348014-2481-2-git-send-email-thomas.abraham@linaro.org> <1314348014-2481-3-git-send-email-thomas.abraham@linaro.org> <1314348014-2481-4-git-send-email-thomas.abraham@linaro.org> <1314348014-2481-5-git-send-email-thomas.abraham@linaro.org> <4E579C9B.7030807@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <4E579C9B.7030807@gmail.com> Sender: linux-samsung-soc-owner@vger.kernel.org To: Rob Herring Cc: Thomas Abraham , boojin.kim@samsung.com, kgene.kim@samsung.com, patches@linaro.org, vinod.koul@intel.com, devicetree-discuss@lists.ozlabs.org, jassisinghbrar@gmail.com, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org List-Id: devicetree@vger.kernel.org On Fri, Aug 26, 2011 at 08:16:11AM -0500, Rob Herring wrote: > Thomas, > > On 08/26/2011 03:40 AM, Thomas Abraham wrote: > > + - arm,pl330-peri-reqs: number of actual peripheral requests connected to the > > + dma controller. Maximum value is 32. > > Perhaps could be a bitmask for sparsely populated requests. May not > matter since phandles will define the connections. > > Can be optional and not present means 00 requests (mem-to-mem only). The number of peripheral requests is readable from configuration register zero, so this is discoverable. Why should we put this information into DT if its provided by the hardware? The number of DMA channels available is also configurable by the SoC designer, yet you don't specify that in DT. And there's a whole bunch of other configuration options available to the SoC designer, most of which are discoverable from the configuration registers. So, I don't think you should be specifying the number of requests.