From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758615AbYESRUK (ORCPT ); Mon, 19 May 2008 13:20:10 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759083AbYESRT4 (ORCPT ); Mon, 19 May 2008 13:19:56 -0400 Received: from rtsoft2.corbina.net ([85.21.88.2]:36655 "HELO mail.dev.rtsoft.ru" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with SMTP id S1756050AbYESRTz (ORCPT ); Mon, 19 May 2008 13:19:55 -0400 Date: Mon, 19 May 2008 21:19:50 +0400 From: Anton Vorontsov To: gary.jennejohn@freenet.de Cc: Grant Likely , fabrizio.garetto@gmail.com, linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, dbrownell@users.sourceforge.net, spi-devel-general@lists.sourceforge.net, Guennadi Liakhovetski Subject: Re: [PATCH 3/4] spi: Add OF binding support for SPI busses Message-ID: <20080519171949.GA12616@polina.dev.rtsoft.ru> Reply-To: avorontsov@ru.mvista.com References: <20080516193054.28030.35126.stgit@trillian.secretlab.ca> <20080516193613.28030.13950.stgit@trillian.secretlab.ca> <20080519190900.01ec3b2a@peedub.jennejohn.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Disposition: inline In-Reply-To: <20080519190900.01ec3b2a@peedub.jennejohn.org> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 19, 2008 at 07:09:00PM +0200, Gary Jennejohn wrote: > On Mon, 19 May 2008 09:57:21 -0600 > "Grant Likely" wrote: > > > On Mon, May 19, 2008 at 7:17 AM, Guennadi Liakhovetski > > wrote: > > > On Fri, 16 May 2008, Grant Likely wrote: > > > > > >> + However, the binding does not attempt to define the specific method for > > >> + assigning chip select numbers. Since SPI chip select configuration is > > >> + flexible and non-standardized, it is left out of this binding with the > > >> + assumption that board specific platform code will be used to manage > > >> + chip selects. Individual drivers can define additional properties to > > >> + support describing the chip select layout. > > > > > > Yes, this looks like a problem to me. This means, SPI devices will need > > > two bindings - OF and platform?... Maybe define an spi_chipselect > > > OF-binding? > > > > Actually, spi devices have *neither*. :-) They bind to the SPI bus. > > Not the platform bus or of_platform bus. But that is Linux internal > > details; this discussion is about device tree bindings. > > > > Note that I did say that drivers can define additional properties for > > supporting chip select changes as needed. I'm just not attempting to > > encode them into the formal binding. There is simply just too many > > different ways to manipulate chip select signals and so I don't feel > > confident trying to define a *common* binding at this moment in time. > > At some point in the future when we have a number of examples to > > choose from then we can extend this binding with chip select related > > properties. > > > > As for the Linux internals, the 5200 SPI bus driver that I posted > > exports a function that allows another driver to call in and > > manipulated the CS lines before the transfer. It isn't the prettiest > > solution, but I'm not locked into the approach and that gives some > > time to consider cleaner interfaces. > > > > I sort of hesitate to hijack this thread, but since we're discussing SPI > and chip selects... > > I have a driver for the SPI controller in the 440EPx. This controller > is very simple and does not have any internal support for a chip select. > The controller seems to also be in the 440GR and 440EP, and may be in > other AMCC CPUs too. > > All chip selects must be done using GPIO. In fact, the board for which > I developed this driver, a modified sequoia, actually uses 2 chip selects. > > My problem was, and is, that there's no generic GPIO support for powerpc. > At least, not that I'm aware of. Please tell me if I'm wrong. Documentation/powerpc/booting-without-of.txt VIII - Specifying GPIO information for devices. And include/linux/of_gpio.h + drivers/of/gpio.c. Soon I'll post some patches for mpc83xx_spi showing how to use GPIOs for the SPI chip selects. -- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2