Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754208Ab3JOHgh (ORCPT ); Tue, 15 Oct 2013 03:36:37 -0400 Received: from comal.ext.ti.com ([198.47.26.152]:48055 "EHLO comal.ext.ti.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752508Ab3JOHge (ORCPT ); Tue, 15 Oct 2013 03:36:34 -0400 Message-ID: <525CF052.4060508@ti.com> Date: Tue, 15 Oct 2013 13:05:46 +0530 From: Sricharan R User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120410 Thunderbird/11.0.1 MIME-Version: 1.0 To: Santosh Shilimkar CC: Rob Herring , , , , , , , , , , , , , Subject: Re: [RFC PATCH 0/6] DRIVERS: IRQCHIP: Add support for crossbar IP References: <1380549564-31045-1-git-send-email-r.sricharan@ti.com> <52499441.1030403@gmail.com> <524AAE69.8060703@ti.com> <524AD290.207@gmail.com> <524AD4B7.7040700@ti.com> <524AE1FA.2050104@gmail.com> <524AE536.5080307@ti.com> In-Reply-To: <524AE536.5080307@ti.com> 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: 5103 Lines: 102 Hi Thomas, On Tuesday 01 October 2013 08:37 PM, Santosh Shilimkar wrote: > On Tuesday 01 October 2013 10:53 AM, Rob Herring wrote: >> On 10/01/2013 08:57 AM, Santosh Shilimkar wrote: >>> On Tuesday 01 October 2013 09:48 AM, Rob Herring wrote: >>>> On 10/01/2013 06:13 AM, Sricharan R wrote: >>>>> Hi, >>>>> >>>>> On Monday 30 September 2013 08:39 PM, Rob Herring wrote: >>>>>> On 09/30/2013 08:59 AM, Sricharan R wrote: >>>>>>> Some socs have a large number of interrupts requests to service >>>>>>> the needs of its many peripherals and subsystems. All of the interrupt >>>>>>> requests lines from the subsystems are not needed at the same >>>>>>> time, so they have to be muxed to the controllers appropriately. >>>>>>> In such places a interrupt controllers are preceded by an >>>>>>> IRQ CROSSBAR that provides flexibility in muxing the device interrupt >>>>>>> requests to the controller inputs. >>>>>>> >>>>>>> This series models the peripheral interrupts that can be routed through >>>>>>> the crossbar to the GIC as 'routable-irqs'. The routable irqs are added >>>>>>> in a separate linear domain inside the GIC. The registered routable domain's >>>>>>> callback are invoked as a part of the GIC's callback, which in turn should >>>>>>> allocate a free irq line and configure the IP accordingly. So every peripheral >>>>>>> in the dts files mentions the fixed crossbar number as its interrupt. A free >>>>>>> gic line for that gets allocated and configured when the peripheral's interrupt >>>>>>> is mapped. >>>>>>> >>>>>>> The minimal crossbar driver to track and allocate free GIC lines and configure the >>>>>>> crossbar is added here, along with the DT bindings. >>>>>> Seems like interrupt-map property is what you need here. >>>>>> >>>>>> http://devicetree.org/Device_Tree_Usage#Advanced_Interrupt_Mapping >>>>>> >>>>>> Versatile Express also has an example. >>>>> OK, but the idea was not to tie up the crossbar<->interrupt numbers at the >>>>> DTS level, but to assign it dynamically during runtime. This was one of the >>>>> comments that came up with first crossbar support patches, which was assigning a >>>>> interrupt line to crossbar number in the DTS and setting it up in crossbar probe. >>>> Is there an actual usecase on a single h/w design that you run out of >>>> interrupts and it is a user decision which interrupts to use? >>>> >>> Yes. There are 240 peripheral interrupts connected out of which 160 can >>> be used in this specific case. >> Yes, I understand the SOC connections. That does not answer my question. >> The 240 interrupts are likely to be limited to fewer by board design, >> pinmuxing, etc. >> > yes limited by different board designs ... > >> How do you handle the 161st interrupt request? Will never happen? Just >> rely on the random driver probe ordering? >> > Well the board dts are expected to provide the peripheral support info to optimise it. > If a board actually has more than 160 peripherals available then in that > case the 161 interrupt will not be mapped. > >>>> You could fill in the interrupt-map at run-time. It would have to be >>>> early (bootloader or early kernel init) and can't be at request_irq time. >>>> >>> Well all options are tried before coming up to the $subject solution. >>> It was suggested by Thomas in the last review. >>> >>>>> https://lkml.org/lkml/2013/7/18/416 >>>>> >>>>> Since this approach of assigning in DTS was opposed, we moved to IRQCHIP and >>>>> that did not go as well. Finally was asked to handle this as a part of GIC driver with >>>>> a separate domain. >>>>> >>>>> http://www.spinics.net/lists/linux-omap/msg97085.html >>>> This has nothing to do with the GIC, so it does not belong there. >>>> >>> Well the router makes connections from peripheral to GIC. Thomas can >>> better explain it but I think since its doing irq routing for GIC on >>> a given hardware, I don't see any issue having some generic map/unmap >>> function in GIC. The actual implementation is still outside of GIC. >> I read Thomas' reply as don't put this crap in his code. >> > That was for the IRQCHIP based approach and as part of that review > Thomas suggested why not irqdomain and suggested a prototype code > as well. > >> You can call it generic, but it is not. It is specific to the GIC and >> looks like an abuse of irqdomains to me. Look where the function >> declaration for register_routable_domain_ops is. >> > I am not sure why you call it abuse of irqdomain since the map/unmap > are exactly the interfaces where the logical to physical irq > connections are made. Look at existing GIC code as well. I still > let Thomas give his expert comment whether it is abusive because it > it was, am sure he wouldn't have suggested that. Is this inline with what you were suggesting and is this approach fine ? Regards, Sricharan -- 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/