Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752723AbbLMVHX (ORCPT ); Sun, 13 Dec 2015 16:07:23 -0500 Received: from down.free-electrons.com ([37.187.137.238]:60713 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752409AbbLMVHV (ORCPT ); Sun, 13 Dec 2015 16:07:21 -0500 Date: Sun, 13 Dec 2015 22:07:19 +0100 From: Maxime Ripard To: Marcus Weseloh Cc: linux-sunxi@googlegroups.com, Rob Herring , Pawel Moll , Mark Rutland , Ian Campbell , Kumar Gala , Chen-Yu Tsai , Mark Brown , devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Subject: Re: [PATCH v2] spi: dts: sun4i: Add support for inter-word wait cycles using the SPI Wait Clock Register Message-ID: <20151213210719.GC19456@lukather> References: <1449873940-10167-1-git-send-email-mweseloh42@gmail.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="H8ygTp4AXg6deix2" Content-Disposition: inline In-Reply-To: <1449873940-10167-1-git-send-email-mweseloh42@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2989 Lines: 76 --H8ygTp4AXg6deix2 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi, On Fri, Dec 11, 2015 at 11:45:39PM +0100, Marcus Weseloh wrote: > Adds support and binding documentation for a new slave device property > "sun4i,spi-word-wait-ns" that allows to set a hardware based delay > between the transmission of words using the SPI Wait Clock Register. > The SPI hardware needs 3 clock cycles to set up the delay, which makes > the minimum non-zero wait time 4 clock cycles. >=20 > Signed-off-by: Marcus Weseloh > --- > Changes from v1: > * renamed the property for more clarity > * wait time is set in nanoseconds instead of number of clock cycles > * transparently handle the 3 setup clock cycles >=20 > There is one review comment that I didn't address: Rob Herring suggested > that this should be in the core-binding rather than in sun4i. I checked > many of the hardware manuals of other SPI drivers and it looks to me like > this hardware based inter-word delay is a feature that not many SPI > controllers offer. And the SPI core currently has no way to control an > inter-word delay, only inter-message. So I would like to propose this aga= in > as a sun4i binding, as it targets a sun4i (or sunxi?) specific hardware > feature. Only a few of them justify to have this in the framework. There's a bunch of controllers that support such a feature, and it definitely belongs in the core. The point of the framework is not to be the least common denominator, it's about having as much code in common as possible, and it definitely falls into that category. Thanks, Maxime --=20 Maxime Ripard, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com --H8ygTp4AXg6deix2 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBAgAGBQJWbd4HAAoJEBx+YmzsjxAgU7QP/A6hcy1/30UnBj0FyQbHUbhy BmumwoOLae03bCY3cTcq4nFiUYz3EHhu2hgNP9QH5NAEmokyd9YxbCV782jSdb8Q 3X791vo8q9I/3cMghElPPiIXM05ENwVPVpnZnxuHAHScJ+AT1q5MsgAy2X+Rktyd +H/JzMvNtducYwtc7dTBCa8KpWfLyv4UQI4WHhntG5LR5OgZLlTqdWPuQWwy0hCl rWoYvw7wV+u1DApAfAmGWyhhpIFxSGfdNbgXY1GYvs6H/RNxF7fV09c8GpMi7ghQ tEOgBW8bF1n2LKBu5lUGHCt+8wujPj4n10SiVB3UZwM5PyRaJidhmqHQ9hP9hgX4 vLyNXg8vCe8aOwKxRnOR41TPCn6tfsyrUVxIpGU2BZxS1phys5kOW8CviVNY0iIg FDpuQNMVC6LaYDDPKAL6nfB69Nrr9hPWaqB/rH885sUzTh5Ek4R9k0+VaeVS6feh 335C7z2C8nF/dqdAlcNY2c1mZWiQCpo5dJxgm6frFZXOMCrzLLhx1v7Wb/xdL+Hk ttAeanEtibt9/xpS2606/iFz0kW4bXHXOuxQLiBqmofyh+M2o9YVkv4QCAnvB/2M qEBDxY21KGiLRa/ivHTTnijaKSB5srUUCxH9YJrp/KUEojnJ0mlOIH1jq9HYwb2P eExrSk8f5PpmQcj/1xpA =+bdG -----END PGP SIGNATURE----- --H8ygTp4AXg6deix2-- -- 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/