From mboxrd@z Thu Jan 1 00:00:00 1970 From: jassi brar Subject: Re: [PATCH 0/7] DMAENGINE: fixes and PrimeCells Date: Fri, 7 May 2010 21:31:40 +0900 Message-ID: References: <1272848060-28049-1-git-send-email-linus.walleij@stericsson.com> <20100507093256.GB19936@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: Received: from mail-vw0-f46.google.com ([209.85.212.46]:54029 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754588Ab0EGMbm (ORCPT ); Fri, 7 May 2010 08:31:42 -0400 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Linus Walleij Cc: Russell King - ARM Linux , Ben Dooks , Dan Williams , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org On Fri, May 7, 2010 at 8:43 PM, Linus Walleij wrote: > 2010/5/7 Russell King - ARM Linux : >> Or let me put it another way - if people are happy for Linux to support >> new ARM CPU architectures, but with very little attention given to DMA >> support on those architectures, then feel free to box the ARM platforms >> into a corner on DMA support - but on the understanding that _you_ will >> have to deal with the DMA API breakage on those architectures yourself. >> Because with ARM platforms not having DMA support, there's absolutely >> no way to run any checks what so ever on DMA when the CPU architecture >> support is created. > > I'm doing the best I can to meet exactly this goal. The changes done in > the DMA engine were done towards the end of making the DMA > engine support *any* DMA controller for the PrimeCells, with due respect, I think DMA Engine API is very restricting. And it is not just the 'async' character of it but also some desirable features like Circular-Linked-Buffer are missing. It may be good enough for Mem->Mem but is found wanting for Mem<->Dev transfers. I would like to see some new API defined that address reasonable requirements of extant platform specific implementations. > So now I guess I have to make it tick on the block known as PL080/PL081 > as well, and I'll have a try at it. I always hoped the pl080 core would be segregated out of S3C implementation, but for some new common DMA API.