From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1032731AbbKEIea (ORCPT ); Thu, 5 Nov 2015 03:34:30 -0500 Received: from metis.ext.4.pengutronix.de ([92.198.50.35]:34646 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030329AbbKEIe3 (ORCPT ); Thu, 5 Nov 2015 03:34:29 -0500 Date: Thu, 5 Nov 2015 09:34:22 +0100 From: Sascha Hauer To: Anton Bondarenko Cc: broonie@kernel.org, b38343@freescale.com, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, vladimir_zapolskiy@mentor.com, jiada_wang@mentor.com Subject: Re: [PATCH v3 1/7] spi: imx: Fix DMA transfer Message-ID: <20151105083422.GH8526@pengutronix.de> References: <1446388901-6073-1-git-send-email-anton.bondarenko.sama@gmail.com> <1446388901-6073-2-git-send-email-anton.bondarenko.sama@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1446388901-6073-2-git-send-email-anton.bondarenko.sama@gmail.com> X-Sent-From: Pengutronix Hildesheim X-URL: http://www.pengutronix.de/ X-IRC: #ptxdist @freenode X-Accept-Language: de,en X-Accept-Content-Type: text/plain X-Uptime: 09:31:00 up 18 days, 17:09, 51 users, load average: 0.23, 0.09, 0.10 User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: sha@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Nov 01, 2015 at 03:41:35PM +0100, Anton Bondarenko wrote: > From: Anton Bondarenko > > RX DMA tail data handling doesn't work correctly in many cases with > current implementation. It happens because SPI core was setup > to generates both RX watermark level and RX DATA TAIL events > incorrectly. SPI transfer triggering for DMA also done in wrong way. > > SPI client wants to transfer 70 words for example. The old DMA > implementation setup RX DATA TAIL equal 6 words. In this case > RX DMA event will be generated after 6 words read from RX FIFO. > The garbage can be read out from RX FIFO because SPI HW does > not receive all required words to trigger RX watermark event. > > New implementation change handling of RX data tail. DMA is used to process > all TX data and only full chunks of RX data with size aligned to FIFO/2. > Driver is waiting until both TX and RX DMA transaction done and all > TX data are pushed out. At that moment there is only RX data tail in > the RX FIFO. This data read out using PIO. Have you looked at the RX_DMA_LENGTH and RXTDEN fields of the DMA register? These seem to be for handling the remaining bytes of a DMA transfer which do not reach the watermark level. From reading the documentation I haven't really understood how it works though. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |