Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752729AbaDDMjk (ORCPT ); Fri, 4 Apr 2014 08:39:40 -0400 Received: from mail-yk0-f169.google.com ([209.85.160.169]:34295 "EHLO mail-yk0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752224AbaDDMjg (ORCPT ); Fri, 4 Apr 2014 08:39:36 -0400 MIME-Version: 1.0 In-Reply-To: References: <1396523431-14519-1-git-send-email-harinik@xilinx.com> <1396523431-14519-2-git-send-email-harinik@xilinx.com> <20140403213446.GB14763@sirena.org.uk> <20140404100919.GO14763@sirena.org.uk> Date: Fri, 4 Apr 2014 18:09:35 +0530 Message-ID: Subject: Re: [PATCH v2 2/2] devicetree: Add devicetree bindings documentation for Cadence SPI From: Harini Katakam To: Peter Crosthwaite Cc: Mark Brown , Grant Likely , Rob Herring , Pawel Moll , Mark Rutland , "ijc+devicetree@hellion.org.uk" , Kumar Gala , linux-spi@vger.kernel.org, "linux-kernel@vger.kernel.org" , "devicetree@vger.kernel.org" , "linux-doc@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, On Fri, Apr 4, 2014 at 5:54 PM, Peter Crosthwaite wrote: > On Fri, Apr 4, 2014 at 10:14 PM, Harini Katakam > wrote: >> Hi Mark, >> >> On Fri, Apr 4, 2014 at 3:39 PM, Mark Brown wrote: >>> On Fri, Apr 04, 2014 at 08:30:38AM +0530, Harini Katakam wrote: >>>> On Fri, Apr 4, 2014 at 3:04 AM, Mark Brown wrote: >>>> > On Thu, Apr 03, 2014 at 04:40:31PM +0530, Harini Katakam wrote: >>> >>>> >> +Optional properties: >>>> >> +- num-cs : Number of chip selects used. >>> >>>> > How does this translate to the hardware? >>> >>>> This IP can drive 4 slaves. >>>> The CS line to be driven is selected in spi device structure and >>>> that is driven by the software. >>> >>> So why specify this in the binding at all? If the device always has the >>> same number of chip selects it's redundant. >> >> I'm sorry, I should have explained that better. >> The IP can support upto 4 chip selects. >> The num-cs value here is the number of chip selects actually used on the board. >> > > Just to clarify - do you mean SoC or board level? > I mean board level. One more reason it will be useful to keep this property is because there is support for adding a decoder where extended slaves can be selected through the IP's control register. (This is not currently implemented in the driver but will be in the future.) Regards, Harini -- 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/