Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760389Ab3HOU1j (ORCPT ); Thu, 15 Aug 2013 16:27:39 -0400 Received: from arroyo.ext.ti.com ([192.94.94.40]:39239 "EHLO arroyo.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760249Ab3HOU1h (ORCPT ); Thu, 15 Aug 2013 16:27:37 -0400 Message-ID: <520D398D.9040806@ti.com> Date: Thu, 15 Aug 2013 16:26:53 -0400 From: Santosh Shilimkar User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/17.0 Thunderbird/17.0 MIME-Version: 1.0 To: Linus Walleij CC: Sricharan R , Tony Lindgren , Nishanth Menon , "linux-kernel@vger.kernel.org" , "devicetree-discuss@lists.ozlabs.org" , "linux-doc@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , Linux-OMAP , Russell King - ARM Linux , Rajendra Nayak , Felipe Balbi , Thomas Gleixner , Grant Likely Subject: Re: [PATCH 1/3] misc: Add crossbar driver References: <51E83A4F.5080904@ti.com> <51ED2385.60108@ti.com> <51ED5C66.1010407@ti.com> <51EFFBE1.4090505@ti.com> <51F0031B.1050307@ti.com> <51F00530.9090703@ti.com> <51F02069.3050207@ti.com> <51F0223E.4050008@ti.com> <51F0240F.3050507@ti.com> <20130813081003.GU7656@atomide.com> <520A02BA.4090805@ti.com> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1894 Lines: 48 On Thursday 15 August 2013 04:01 PM, Linus Walleij wrote: > On Tue, Aug 13, 2013 at 11:56 AM, Sricharan R wrote: > >> Initially irqchip was discussed, but we also have a DMA crossbar >> to map the dma-requests. Since both irq/dma crossbars should be handled, >> pinctrl was suggested as the appropriate place to handle this. > > I think it is better to use irqchip. > Did you happen to read the thread why irqchip is in-appropriate for such an IP. As I said earlier, an IRQ-chip always need a real IRQ link (even for the chained one) to the primary irqchip. This IP is just dummy IP makes the connections for the primary irqchip(read GIC). And its use only limited to make the connection between the peripheral IRQ event to the GIC IRQ line. I don't see how you can make this happen with an irqchip infrastructure. If you have a idea to make that work, we can go with that since for time being we can ignore the DMA event related need of this IP. > For DMA there is already an arbiter mechanism for arbitration of > virtual channels over physical channels, this is not much different, > the DMA might need some different tweaking but should be solved > in that subsystem I think. > Sure. The IP won't be limited to DMA and IRQ lines but any other events like gpio etc in future. > I don't see any way to really abstract this pretty simple crossbar > for reuse across subsystems. > This exactly the reason, i am against idea of over-engineering the simple IP whose only job is to make the physical wire connection in software where as this is generally done in RTL by default on most of the SOCs. Regards, Santosh -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/