From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaro Koskinen Subject: Re: [PATCH] OMAP: McSPI: Fix RX DMA transfer path Date: Mon, 15 Jun 2009 11:37:53 +0300 Message-ID: <4A360861.9040403@nokia.com> References: <> <1244809910-4014-1-git-send-email-aaro.koskinen@nokia.com> <005a01c9ed7a$2a5227b0$LocalHost@wipultra793> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp.nokia.com ([192.100.105.134]:18457 "EHLO mgw-mx09.nokia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750767AbZFOIiq (ORCPT ); Mon, 15 Jun 2009 04:38:46 -0400 In-Reply-To: <005a01c9ed7a$2a5227b0$LocalHost@wipultra793> Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: ext Hemanth V Cc: "dbrownell@users.sourceforge.net" , "spi-devel-general@lists.sourceforge.net" , "linux-omap@vger.kernel.org" , "Nurkkala Eero.An (EXT-Offcode/Oulu)" Hello, ext Hemanth V wrote: > From: "Aaro Koskinen" >> From: Eero Nurkkala >> >> When data is read through DMA, the last element must be read separately >> through the RX register. It cannot be transferred by the DMA. For further >> details see e.g. OMAP3430 TRM. > > Could you provide the section number and the version of TRM you are > referring to. Table 19-16 and section 19.6.2.5.1 in the public TRM. >> Without the fix the driver causes extra clocks to be clocked to the >> bus after DMA RX operations. This can cause interesting behaviour with >> some devices. > > Could you provide more details on the errors seen i.e is the transfer > aborted There is an extra word, which a device can interpret as a command. Also if the word size != command size the device can hang. Unless the device hangs, you may not even notice anything. A.