Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753364AbaDDOaX (ORCPT ); Fri, 4 Apr 2014 10:30:23 -0400 Received: from mail-yh0-f52.google.com ([209.85.213.52]:46769 "EHLO mail-yh0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753278AbaDDOaU (ORCPT ); Fri, 4 Apr 2014 10:30:20 -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> <20140404124637.GT14763@sirena.org.uk> Date: Fri, 4 Apr 2014 20:00:19 +0530 Message-ID: Subject: Re: [PATCH v2 2/2] devicetree: Add devicetree bindings documentation for Cadence SPI From: Harini Katakam To: Mark Brown Cc: 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 7:38 PM, Harini Katakam wrote: > Hi Mark, > > On Fri, Apr 4, 2014 at 6:16 PM, Mark Brown wrote: >> On Fri, Apr 04, 2014 at 05:44:23PM +0530, Harini Katakam wrote: >>> 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: >> >>> >> 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. >> >> Why does that need to be configured? Surely the presence of slaves is >> enough information. > > OK. I understand. > Can you comment on the case where a decoder is used? > > 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.) > > How should the driver know whether it is 4 or 16 select lines for example? > This has to be written to master->num_chipselect. > > Regards, > Harini Just adding to my above comment. Alternately, I could not use the "num-cs" property and add another optional property to be used only when required. The driver sets a default value already. 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/