Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754217Ab3DLQNc (ORCPT ); Fri, 12 Apr 2013 12:13:32 -0400 Received: from mail-wg0-f44.google.com ([74.125.82.44]:46212 "EHLO mail-wg0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752409Ab3DLQNb (ORCPT ); Fri, 12 Apr 2013 12:13:31 -0400 Date: Fri, 12 Apr 2013 17:13:25 +0100 From: Lee Jones To: Rabin Vincent Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, arnd@arndb.de, linus.walleij@stericsson.com Subject: Re: [PATCH 3/8] dmaengine: ste_dma40: Actually write the runtime configuration to registers Message-ID: <20130412161325.GB18459@gmail.com> References: <1365532783-27425-1-git-send-email-lee.jones@linaro.org> <1365532783-27425-3-git-send-email-lee.jones@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1402 Lines: 32 On Fri, 12 Apr 2013, Rabin Vincent wrote: > 2013/4/9 Lee Jones : > > Someone has spent a fair amount of effort writing a runtime configuration > > changing algorithm for DMA clients. However, the config appears to never > > actually make it to hardware. In order for the configuration to take hold > > we need to issue a d40_config_write(), as this is the routine which writes > > it into the hardware's registers. > > No, it's not. This function is only for initial configuration which > should only be written when the channel is allocated. In fact, by > calling it here in runtime_config, you are introducing a serious bug: > other logical channels on the same physical channel will stop because of > the SSLNK/SDLNK of the physical channel being zeroed. > > The runtime config already makes it the hardware in the existing code, > via d40_*_cfg(). Ah, I see. I'll move it all back and investigate my bug further then. Thanks for taking the time to write such a well written review. -- Lee Jones Linaro ST-Ericsson Landing Team Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog -- 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/