From mboxrd@z Thu Jan 1 00:00:00 1970 From: Arnd Bergmann Subject: Re: [PATCH 15/30] usb/musb: use a Kconfig choice to pick the right DMA method Date: Sun, 02 Oct 2011 20:00:31 +0200 Message-ID: <1757336.Qk72n3s00p@wuerfel> References: <1317566760-25681-1-git-send-email-arnd@arndb.de> <1317566760-25681-16-git-send-email-arnd@arndb.de> <20111002161447.GC12323@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20111002161447.GC12323@n2100.arm.linux.org.uk> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: linux-arm-kernel-bounces@lists.infradead.org Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=m.gmane.org@lists.infradead.org To: linux-arm-kernel@lists.infradead.org Cc: Tony Lindgren , linux-omap@vger.kernel.org, Russell King - ARM Linux , linux-kernel@vger.kernel.org, Felipe Balbi List-Id: linux-omap@vger.kernel.org On Sunday 02 October 2011 17:14:47 Russell King - ARM Linux wrote: > On Sun, Oct 02, 2011 at 04:45:45PM +0200, Arnd Bergmann wrote: > > The logic to allow only one DMA driver in MUSB is currently > > flawed, because it also allows picking no DMA driver at all > > and also not selecting PIO mode. > > > > Using a choice statement makes this foolproof for now and > > also simplifies the Makefile. > > > > Unfortunately, we will have to revisit this when we start > > supporting multiple ARM platforms in a single kernel binary, > > because at that point we will actually need to select > > multiple DMA drivers and pick the right one at run-time. > > I thought there was some work going on to convert this to use the > dmaengine stuff? That would certainly be the best solution here, I wasn't aware that it has already been discussed. Unfortunately, even with the dma parts out of the way there is a lot that needs to be done to make musb, ehci or ohci really cross-platform. Right now, you can only have one platform driver glue for each of those drivers, and they should eventually be converted to a large library module for the core, with independent platform driver front-end, similar to the recent conversion of the sdhci driver by Shawn Guo, and the way that a lot of the other common drivers work. Arnd