From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760086AbaGYIis (ORCPT ); Fri, 25 Jul 2014 04:38:48 -0400 Received: from mout.kundenserver.de ([212.227.17.10]:53734 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758985AbaGYIiq (ORCPT ); Fri, 25 Jul 2014 04:38:46 -0400 From: Arnd Bergmann To: Mika Westerberg Cc: linux-arm-kernel@lists.infradead.org, Kweh Hock Leong , Eric Miao , Russell King , Haojian Zhuang , Mark Brown , Chew Chiau Ee , Darren Hart , chiauee85@gmail.com, linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org, Andy Shevchenko Subject: Re: [PATCH] spi/pxa2xx-pci: Enable DMA binding through device name Date: Fri, 25 Jul 2014 10:38:36 +0200 Message-ID: <7309109.iKHmHOxjzD@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.11.0-18-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20140725082249.GX1857@lahna.fi.intel.com> References: <1406196111-22861-1-git-send-email-hock.leong.kweh@intel.com> <5574058.fMy2hcvT92@wuerfel> <20140725082249.GX1857@lahna.fi.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V02:K0:ikyCD7ClGIkSwz7MUh/ITOIAdbNVyV7NkwkMZtSNMe3 A5UoCxkcWj38znQXUloWg/eTy4ZvFTZJhoZt9X57CF9CpYorA8 Rfkw7FH1GmuFgo/H7KiKAzowGnsrg/4r0mtJY7xmQmOjdDasCE GWwo+L0IFpn6IYXFyrpjpIKgLdnlX423EqQpp9Y6ORCZiLgkb0 zA7QTI/caN3vqUDJF+w7pIlWnM5cdw1z5zD62RO7ECaw0iQHOl NARfHe1ukrulTEHuDBZgp82jvvSP5YCeH5bIzr5hhp7WHOskRR gCM74KACTB1c6zWqJEjbErShj5wlt5q5+z9nbbtOPBXIj+3vHf IcJEh6lqCZKYsElGgMRo= Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Friday 25 July 2014 11:22:49 Mika Westerberg wrote: > > All you need to do is change your filter function to take the > > slave id from pxa_spi_info and stick it in there, e.g. > > > > static bool pxa2xx_spi_dw_dma_filter(struct dma_chan *chan, void *param) > > { > > const struct pxa2xx_spi_master *pdata = param; > > struct dw_dma_chan *dwc = to_dw_dma_chan(chan); > > > > dwc->request_line = fargs->req; > > dwc->src_master = 0; > > dwc->dst_master = 0; > > > > return 1; > > } > > Oh man. That makes pxa2xx_spi dependent on a certain specific DMA engine > driver. I think you can improve this by putting the filter function (and a pointer to it) into the pxa2xx_spi_master data provided by the PCI driver. On ARM, we usually provide those pointers through platform_data from the board file. > > Note that the filter function by definition is specific to the dma > > controller, not the dma slave (that's why most people define it in > > the dmaengine driver), and the pxa2xx_spi_dma_filter() function used > > in spi-pxa2xx-dma.c looks like it was written for another dma engine: > > I wonder what's the rationale that passing slave_id with > dma_slave_config is wrong? The current code works fine with that and is > is independent of the DMA engine driver (even though we know that it is > going to be dw-dma). > > The dw-dma handles slave_id in its implementation of > dmaengine_slave_config(). The main point is that a single 'slave_id' is not actually enough to identify what a slave needs. In case of dw_dma, the dma engine actually requires three numbers (request line, source master, destination master) to identify it, and there is no good way to put all that information into a single integer. Other dma engines require a different set of data. There are only two drivers left that actually use slave_id in this way, and only for the legacy (no DT or ACPI) case, every other driver uses either DT or a filter function. I believe the shmobile part will soon be done with, after shmobile has been converted to DT, and after that we should remove the slave_id field from the dma_slave_config interface. Arnd