From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Jarzmik Subject: Re: [PATCH V3 1/2] of: Add generic device tree DMA helpers Date: Fri, 20 Jul 2012 11:08:44 +0200 Message-ID: <87y5meu7dv.fsf@free.fr> References: <1335820679-28721-1-git-send-email-jon-hunter@ti.com> <201206271520.49276.arnd@arndb.de> <1342161907.1726.26.camel@vkoul-udesk3> <201207171924.33756.arnd@arndb.de> <1342756850.1726.74.camel@vkoul-udesk3> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from smtp1-g21.free.fr ([212.27.42.1]:56743 "EHLO smtp1-g21.free.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752939Ab2GTJJN (ORCPT ); Fri, 20 Jul 2012 05:09:13 -0400 Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Vinod Koul Cc: Arnd Bergmann , Stephen Warren , Benoit Cousson , Stephen Warren , device-tree , Nicolas Ferre , Rob Herring , Grant Likely , Jassi Brar , Jon Hunter , Russell King - ARM Linux , dan.j.williams@intel.com, linux-omap , linux-arm-kernel@lists.infradead.org Vinod Koul writes: >> 4. A dma controller requiring complex configuration: >> >> dma: dmaengine@48000000 { >> compatible = "foo,foo-sdma" >> reg = <0x48000000 0x1000>; >> interrupts = <4>; >> #dma-cells = <6>; /* phandle, flag, request, channel, >> input-width, output-width */ > Why would we want the widths to be here? > Assuming a DMA from System memory to a peripheral, source width should > be system memory width and destination the peripheral width. IMO these > should not be in dma property even if we need these Hi Vinod, I know at least one peripheral which accepts 2 widths, 8bit and 16bit, namely the M-Systems DiskOnChip G3 NAND chip. This device has to configured to choose either 8bit data bus access or 16bit data bus access. I'm just wondering if that usecase will fit in without the width information embedded, and how will the driver choose the width to use ? Cheers. -- Robert From mboxrd@z Thu Jan 1 00:00:00 1970 From: robert.jarzmik@free.fr (Robert Jarzmik) Date: Fri, 20 Jul 2012 11:08:44 +0200 Subject: [PATCH V3 1/2] of: Add generic device tree DMA helpers References: <1335820679-28721-1-git-send-email-jon-hunter@ti.com> <201206271520.49276.arnd@arndb.de> <1342161907.1726.26.camel@vkoul-udesk3> <201207171924.33756.arnd@arndb.de> <1342756850.1726.74.camel@vkoul-udesk3> Message-ID: <87y5meu7dv.fsf@free.fr> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Vinod Koul writes: >> 4. A dma controller requiring complex configuration: >> >> dma: dmaengine at 48000000 { >> compatible = "foo,foo-sdma" >> reg = <0x48000000 0x1000>; >> interrupts = <4>; >> #dma-cells = <6>; /* phandle, flag, request, channel, >> input-width, output-width */ > Why would we want the widths to be here? > Assuming a DMA from System memory to a peripheral, source width should > be system memory width and destination the peripheral width. IMO these > should not be in dma property even if we need these Hi Vinod, I know at least one peripheral which accepts 2 widths, 8bit and 16bit, namely the M-Systems DiskOnChip G3 NAND chip. This device has to configured to choose either 8bit data bus access or 16bit data bus access. I'm just wondering if that usecase will fit in without the width information embedded, and how will the driver choose the width to use ? Cheers. -- Robert