Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751530AbcKYVIj (ORCPT ); Fri, 25 Nov 2016 16:08:39 -0500 Received: from mail.blih.net ([212.83.177.182]:55338 "EHLO mail.blih.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750916AbcKYVI2 (ORCPT ); Fri, 25 Nov 2016 16:08:28 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=bidouilliste.com; h=date :from:to:cc:subject:message-id:in-reply-to:references :mime-version:content-type:content-transfer-encoding; q=dns; s= mail; b=NHHrWadxuIKV3TvGavDlYj42cLQ8sPVLLvQOBL4kumpLW1jWwbvHIjXr blunFbliwek0VCcxkGjybOS/kI+SOu+LmCghNakVkzcQFHM6nym2ceYQpAuhaM9t 56wLUBXDvmPWNXZU/sjn+B519cY3yqzzzgeCW7TvMpDlaWniZV0= Date: Fri, 25 Nov 2016 22:07:52 +0100 From: Emmanuel Vadot To: Maxime Ripard Cc: mark.rutland@arm.com, devicetree@vger.kernel.org, linux@armlinux.org.uk, linux-kernel@vger.kernel.org, wens@csie.org, robh+dt@kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] ARM: dts: sunxi: Add num-cs for A20 spi nodes Message-Id: <20161125220752.c989c85e01ed202be0485c78@bidouilliste.com> In-Reply-To: <20161125152047.oadxi2xbgm4kdd7q@lukather> References: <20161122170616.29557-1-manu@bidouilliste.com> <20161124195517.qrq7briu3pwjnp4n@lukather> <20161124210509.be743aae84c26c6c2e666c6e@bidouilliste.com> <20161125152047.oadxi2xbgm4kdd7q@lukather> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.29; amd64-portbld-freebsd12.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1598 Lines: 50 On Fri, 25 Nov 2016 16:20:47 +0100 Maxime Ripard wrote: > On Thu, Nov 24, 2016 at 09:05:09PM +0100, Emmanuel Vadot wrote: > > On Thu, 24 Nov 2016 20:55:17 +0100 > > Maxime Ripard wrote: > > > > > On Tue, Nov 22, 2016 at 06:06:16PM +0100, Emmanuel Vadot wrote: > > > > The spi0 controller on the A20 have up to 4 CS (Chip Select) while the > > > > others three only have 1. > > > > Add the num-cs property to each node. > > > > > > > > Signed-off-by: Emmanuel Vadot > > > > > > I don't think we have any code that uses it at the moment. What is the > > > rationale behind this patch? > > > > > > Thanks! > > > Maxime > > > > > > -- > > > Maxime Ripard, Free Electrons > > > Embedded Linux and Kernel engineering > > > http://free-electrons.com > > > > Hi Maxime, > > > > If num-cs isn't present nothing prevent to start a transfer with a > > non-valid CS pin, resulting in an error. > > num-cs are default property especially made for this and a SPI driver > > should try to get the property at probe/attach time. > > Yes, but as far as I know, our driver doesn't. I'm all in for having > support for that in our driver, but without it, that patch is kind of > useless. > > Maxime > > -- > Maxime Ripard, Free Electrons > Embedded Linux and Kernel engineering > http://free-electrons.com Yes the Linux driver doesn't use it but my upcoming one for FreeBSD uses it. So it is not useless for downstream user of DTS. Cheers, -- Emmanuel Vadot