From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E00A5C169C4 for ; Fri, 8 Feb 2019 16:58:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A98F520855 for ; Fri, 8 Feb 2019 16:58:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=lunn.ch header.i=@lunn.ch header.b="mVKJUfhG" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727377AbfBHQ6r (ORCPT ); Fri, 8 Feb 2019 11:58:47 -0500 Received: from vps0.lunn.ch ([185.16.172.187]:44195 "EHLO vps0.lunn.ch" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726522AbfBHQ6r (ORCPT ); Fri, 8 Feb 2019 11:58:47 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lunn.ch; s=20171124; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=XrzYbNiWpIzJe3u6TxnTmMcQ9hPdqgWmrHQ2pQFhDeE=; b=mVKJUfhGlC1TAC3NmbtGSOCc5W Joq/2FSVkPooBjOw6pFNkEO8A50YvsW6LBAn3rmkCXK6K6GN4KA4F2m+N3J1HVEuhqFC/Tw0TJffj Gvk4ly0aDvv0K0Kn97Cvy3FK85dx3wfRK2yLT/B43D8/mFSwylM+Zr3k4vdmDRwnQJDM=; Received: from andrew by vps0.lunn.ch with local (Exim 4.89) (envelope-from ) id 1gs9UB-0000Wg-R7; Fri, 08 Feb 2019 17:58:43 +0100 Date: Fri, 8 Feb 2019 17:58:43 +0100 From: Andrew Lunn To: Federico Vaga Cc: Peter Korsgaard , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 1/5] i2c:ocores: stop transfer on timeout Message-ID: <20190208165843.GA1853@lunn.ch> References: <20190208161201.7860-1-federico.vaga@cern.ch> <20190208161201.7860-2-federico.vaga@cern.ch> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190208161201.7860-2-federico.vaga@cern.ch> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 08, 2019 at 05:11:57PM +0100, Federico Vaga wrote: > Detecting a timeout is ok, but we also need to assert a STOP command on > the bus in order to prevent it from generating interrupts when there are > no on going transfers. > > Example: very long transmission. > > 1. ocores_xfer: START a transfer > 2. ocores_isr : handle byte by byte the transfer > 3. ocores_xfer: goes in timeout [[bugfix here]] > 4. ocores_xfer: return to I2C subsystem and to the I2C driver > 5. I2C driver : it may clean up the i2c_msg memory > 6. ocores_isr : receives another interrupt (pending bytes to be > transferred) but the i2c_msg memory is invalid now > > So, since the transfer was too long, we have to detect the timeout and > STOP the transfer. > > Another point is that we have a critical region here. When handling the > timeout condition we may have a running IRQ handler. For this reason I > introduce a spinlock. > > In order to make easier to understan locking I have: > - added a new function to handle timeout > - modified the current ocores_process() function in order to be protected > by the new spinlock > Like this it is obvious at first sight that this locking serializes > the execution of ocores_process() and ocores_process_timeout() > > Signed-off-by: Federico Vaga Reviewed-by: Andrew Lunn Andrew