From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from buildserver.ru.mvista.com (unknown [213.79.90.228]) by ozlabs.org (Postfix) with ESMTP id 258BB1007DE for ; Wed, 18 Nov 2009 10:28:27 +1100 (EST) Date: Wed, 18 Nov 2009 02:28:23 +0300 From: Anton Vorontsov To: Torsten Fleischer Subject: Re: spi_mpc8xxx.c: chip select polarity problem Message-ID: <20091117232823.GA19058@oksana.dev.rtsoft.ru> References: <200911161742.46663.to-fleischer@t-online.de> <20091116171037.GA26163@oksana.dev.rtsoft.ru> <20091116180008.GA6748@oksana.dev.rtsoft.ru> <200911172109.28841.to-fleischer@t-online.de> <20091117202211.GB27574@oksana.dev.rtsoft.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: <20091117202211.GB27574@oksana.dev.rtsoft.ru> Cc: linuxppc-dev@lists.ozlabs.org Reply-To: avorontsov@ru.mvista.com List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Nov 17, 2009 at 11:22:11PM +0300, Anton Vorontsov wrote: > On Tue, Nov 17, 2009 at 09:09:28PM +0100, Torsten Fleischer wrote: > > On Mon, Nov 16, 2009 at 19:00PM, Anton Vorontsov wrote: > > [...] > > > > So it might be better to fix up initial value in the platform code? > > > > > > Oh, we actually cannot, because the driver calls > > > gpio_direction_output(). > > > > > > And since we don't know the mode prior to SPI device's driver > > > probe() finished, we'll have to set up an initial state in the > > > first SPI transfer. I.e. something like this: > > > > In most cases the device drivers perform SPI transfers already in their > > probe() function. How can it be ensured that the CS of all other devices are > > inactive even if they are not initialized at that time? > > Good question. Oh, well... then we have to use spi-cs-high, > no matter that it is a duplication of the 'compatible' property. > SPI bus drivers don't know all the devices and their CS level, > and so spi-cs-high is the only way to tell that information. :-( Oh. On the other hand, we can postpone the gpio_direction_output() call, and still require that the platform code (or firmware) should be responsible for setting a sane default values on the chip selects. -- Anton Vorontsov email: cbouatmailru@gmail.com irc://irc.freenode.net/bd2