Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757661AbZKSWme (ORCPT ); Thu, 19 Nov 2009 17:42:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757556AbZKSWmd (ORCPT ); Thu, 19 Nov 2009 17:42:33 -0500 Received: from caramon.arm.linux.org.uk ([78.32.30.218]:32991 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757395AbZKSWmc (ORCPT ); Thu, 19 Nov 2009 17:42:32 -0500 Date: Thu, 19 Nov 2009 22:41:51 +0000 From: Russell King - ARM Linux To: Wan ZongShun Cc: Andrew Morton , linux-spi , David Brownell-sourceforge , linux-kernel , linux-arm-kernel Subject: Re: [PATCH] ARM: Add spi controller driver support for NUC900 Message-ID: <20091119224151.GF22232@n2100.arm.linux.org.uk> References: <4B024748.9080001@gmail.com> <20091118142109.ff2c5ef6.akpm@linux-foundation.org> <20091118234928.8d86a9f9.akpm@linux-foundation.org> <20091119090204.GB13376@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2065 Lines: 45 On Thu, Nov 19, 2009 at 05:49:22PM +0800, Wan ZongShun wrote: > 2009/11/19 Russell King - ARM Linux : > > On Thu, Nov 19, 2009 at 04:40:50PM +0800, Wan ZongShun wrote: > >> 2009/11/19 Andrew Morton : > >> > I don't know, because I don't know what operation the hardware needs to > >> > stop it from generating interrupts. ?Perhaps that's clk_disable()? > >> > >> The interrupt will be not occur as long as I run clk_disable(). > >> > >> > Once you've stopped the source of interrupts then the code should wait > >> > for the IRQ handler to complete if it's running on another CPU. ?Yes, > >> > free_irq() does that. > >> > >> So, regarding my system of single CPU, maybe I need put this > >> 'clk_disable()' in the front of function of w90p910_spi_remove(). > >> > >> right? > > > > Depending on the hardware, that's not the right answer. ?If turning off > > the clock also causes register accesses to the device to abort, it is > > a very dangerous thing to do. > > > > It can also be dangerous if the clock is used to synchronise the interrupt > > output - it can lead to the output being permanently asserted if the clock > > is turned off with it asserted. > > > > Normally devices have an "interrupt enable" register. ?You should disable > > all interrupts from the device using this register after unregistering > > the driver from the (SPI) subsystem. > > sir, so I need implement a API to disable spi device interrupt by > "interrupt enable" register? > but I did not find the operation in other ARM platform when they close > your spi driver. > > or something I missed? No, I think you need to reverse the effects of w90p910_enable_int() by clearing the ENINT bit. I'm making the assumption that doing so prevents interrupts being generated by the device. -- 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/