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Message-ID: <5286372F.3000302@ti.com>
Date: Fri, 15 Nov 2013 10:01:03 -0500
From: Santosh Shilimkar <santosh.shilimkar@...com>
To: Mark Rutland <mark.rutland@....com>
CC: Sricharan R <r.sricharan@...com>,
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Subject: Re: [PATCH V4 1/4] DRIVERS: IRQCHIP: IRQ-GIC: Add support for routable
irqs
On Friday 15 November 2013 06:23 AM, Mark Rutland wrote:
> On Thu, Nov 14, 2013 at 04:46:36PM +0000, Sricharan R wrote:
>> Hi Mark,
>>
>> On Thursday 14 November 2013 07:31 PM, Mark Rutland wrote:
>>> On Thu, Nov 14, 2013 at 12:18:47PM +0000, Sricharan R wrote:
>>>> In some socs the gic can be preceded by a crossbar IP which
>>>> routes the peripheral interrupts to the gic inputs. The peripheral
>>>> interrupts are associated with a fixed crossbar input line and the
>>>> crossbar routes that to one of the free gic input line.
>>>>
>>>> The DT entries for peripherals provides the fixed crossbar input line
>>>> as its interrupt number and the mapping code should associate this with
>>>> a free gic input line. This patch adds the support inside the gic irqchip
>>>> to handle such routable irqs. The routable irqs are registered in a linear
>>>> domain. The registered routable domain's callback should be implemented
>>>> to get a free irq and to configure the IP to route it.
>>>>
>>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>>> Cc: Linus Walleij <linus.walleij@...aro.org>
>>>> Cc: Santosh Shilimkar <santosh.shilimkar@...com>
>>>> Cc: Russell King <linux@....linux.org.uk>
>>>> Cc: Tony Lindgren <tony@...mide.com>
>>>> Cc: Rajendra Nayak <rnayak@...com>
>>>> Cc: Marc Zyngier <marc.zyngier@....com>
>>>> Cc: Grant Likely <grant.likely@...aro.org>
>>>> Cc: Rob Herring <rob.herring@...xeda.com>
>>>> Signed-off-by: Sricharan R <r.sricharan@...com>
>>>> Acked-by: Santosh Shilimkar <santosh.shilimkar@...com>
>>>> ---
>>>> [V2] Added default routable-irqs functions to avoid
>>>> unnecessary if checks as per Thomas Gleixner comments
>>>> and renamed routable-irq binding as per
>>>> Kumar Gala <galak@...eaurora.org> comments.
>>>>
>>>> [V3] Addressed unnecessary warn-on and updated default
>>>> xlate function as per Thomas Gleixner comments
>>>>
>>>> Documentation/devicetree/bindings/arm/gic.txt | 6 ++
>>>> drivers/irqchip/irq-gic.c | 81 ++++++++++++++++++++++---
>>>> include/linux/irqchip/arm-gic.h | 7 ++-
>>>> 3 files changed, 83 insertions(+), 11 deletions(-)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/arm/gic.txt b/Documentation/devicetree/bindings/arm/gic.txt
>>>> index 3dfb0c0..5357745 100644
>>>> --- a/Documentation/devicetree/bindings/arm/gic.txt
>>>> +++ b/Documentation/devicetree/bindings/arm/gic.txt
>>>> @@ -49,6 +49,11 @@ Optional
>>>> regions, used when the GIC doesn't have banked registers. The offset is
>>>> cpu-offset * cpu-nr.
>>>>
>>>> +- arm,routable-irqs : Total number of gic irq inputs which are not directly
>>>> + connected from the peripherals, but are routed dynamically
>>>> + by a crossbar/multiplexer preceding the GIC. The GIC irq
>>>> + input line is assigned dynamically when the corresponding
>>>> + peripheral's crossbar line is mapped.
>>> I'm not keen on the design of the arm,routable-irqs property. The set of
>>> IRQs which the crossbar IP can use is a property of which IRQ lines it
>>> has routed to the GIC. I don't see why that should be considered a
>>> property of the GIC; it's a property of the crossbar IP's attachment to
>>> the GIC.
>>>
>>> Given we already have a mechanism for describing the attachment (i.e.
>>> the interrupts property) where the property appears on the node for the
>>> device generating/propagating the interrupt, I don't see why we should
>>> do differently here.
>> We did try using interrupts=<> property for all peripherals and
>> mapping them as crossbar's parent. But that approach of representing
>> crossbar as a interrupt parent was not accepted, since the crossbar
>> was just routing the interrupts from peripherals to GIC and nothing more.
>> Also mapping all the interrupts using interrupt-map like property by a fixed way
>> in DTS itself was considered hacky
>
> I'm not suggesting you should interrupt-map. I agree that that
> interrupt-map is not suitable for a dynamically configurable device like
> the crossbar.
>
> When you say that the crossbar is just routing the interrupts, at what
> level is it doing so? Does it accept a logical interrupt and output
> another logical interrupt, or does it just connect the two lines
> electrically?
>
Its just makes electrical connection between input and output line and
thats it.
Regards,
Santosh
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