From mboxrd@z Thu Jan 1 00:00:00 1970 From: mporter@ti.com (Matt Porter) Date: Mon, 1 Oct 2012 12:39:55 -0400 Subject: [RFC PATCH 08/13] mmc: omap_hsmmc: limit max_segs with the EDMA DMAC In-Reply-To: <1348738868.1648.13.camel@vkoul-udesk3> References: <1348152226-13588-1-git-send-email-mporter@ti.com> <1348152226-13588-9-git-send-email-mporter@ti.com> <20120921184721.GD31374@n2100.arm.linux.org.uk> <1348738868.1648.13.camel@vkoul-udesk3> Message-ID: <20121001163955.GO5641@beef> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Sep 27, 2012 at 03:11:08PM +0530, Vinod Koul wrote: > On Fri, 2012-09-21 at 19:47 +0100, Russell King - ARM Linux wrote: > > On Fri, Sep 21, 2012 at 10:45:29PM +0530, S, Venkatraman wrote: > > > On Thu, Sep 20, 2012 at 8:13 PM, Matt Porter wrote: > > > > The EDMA DMAC has a hardware limitation that prevents supporting > > > > scatter gather lists with any number of segments. Since the EDMA > > > > DMA Engine driver sets the maximum segments to 16, we do the > > > > same. > > > > > > > > Note: this can be removed once the DMA Engine API supports an > > > > API to query the DMAC's segment limitations. > > > > > > > > > > I wouldn't want to bind the properties of EDMA to omap_hsmmc as this patch > > > suggests. Why don't we have a max_segs property, which when explicitly specified > > > in DT, will override the default ? > > > > Why not have a generic way that DMA engine can export these kinds of > > properties? > We discussed this at KS. I was of opinion that DMA engine should export > controller and channel capabilities as part of the channel it returns. > > Some folks had an opinion that they already know how to use controller > so may not be very helpful, but if it is going to help (which I think), > i have a patch for this :) Anything you can show at this point? ;) I'd be happy to drop the half-hack for a real API. If not, I'm going to carry that to v2 atm. -Matt