linux-kernel - Re: [PATCH 5/5] ARM: gic: add OF based initialization

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Date:	Fri, 16 Sep 2011 15:04:11 +0530
From:	Thomas Abraham <thomas.abraham@...aro.org>
To:	Rob Herring <robherring2@...il.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	grant.likely@...retlab.ca, marc.zyngier@....com,
	jamie@...ieiles.com, b-cousson@...com, shawn.guo@...aro.org,
	Rob Herring <rob.herring@...xeda.com>
Subject: Re: [PATCH 5/5] ARM: gic: add OF based initialization

Hi Rob,

On 15 September 2011 18:24, Rob Herring <robherring2@...il.com> wrote:
> On 09/15/2011 02:55 AM, Thomas Abraham wrote:
>> Hi Rob,
>>
>> On 14 September 2011 22:01, Rob Herring <robherring2@...il.com> wrote:
>>> From: Rob Herring <rob.herring@...xeda.com>
>>>
>>> This adds gic initialization using device tree data. The initialization
>>> functions are intended to be called by a generic OF interrupt
>>> controller parsing function once the right pieces are in place.
>>>
>>> PPIs are handled using 3rd cell of interrupts properties to specify the cpu
>>> mask the PPI is assigned to.
>>>
>>> Signed-off-by: Rob Herring <rob.herring@...xeda.com>
>>> ---
>>>  Documentation/devicetree/bindings/arm/gic.txt |   53 ++++++++++++++++++++++++
>>>  arch/arm/common/gic.c                         |   55 +++++++++++++++++++++++--
>>>  arch/arm/include/asm/hardware/gic.h           |   10 +++++
>>>  3 files changed, 114 insertions(+), 4 deletions(-)
>>>  create mode 100644 Documentation/devicetree/bindings/arm/gic.txt
>>
>> [...]
>>
>>
>>> diff --git a/arch/arm/common/gic.c b/arch/arm/common/gic.c
>>> index d1ccc72..14de380 100644
>>> --- a/arch/arm/common/gic.c
>>> +++ b/arch/arm/common/gic.c
>>
>> [...]
>>
>>> +void __init gic_of_init(struct device_node *node, struct device_node *parent)
>>> +{
>>> +       void __iomem *cpu_base;
>>> +       void __iomem *dist_base;
>>> +       int irq;
>>> +       struct irq_domain *domain = &gic_data[gic_cnt].domain;
>>> +
>>> +       if (WARN_ON(!node))
>>> +               return;
>>> +
>>> +       dist_base = of_iomap(node, 0);
>>> +       WARN(!dist_base, "unable to map gic dist registers\n");
>>> +
>>> +       cpu_base = of_iomap(node, 1);
>>> +       WARN(!cpu_base, "unable to map gic cpu registers\n");
>>> +
>>> +       domain->nr_irq = gic_irq_count(dist_base);
>>> +       domain->irq_base = irq_alloc_descs(-1, 0, domain->nr_irq, numa_node_id());
>>
>> For exynos4, all the interrupts originating from GIC are statically
>> mapped to start from 32 in the linux virq space (GIC SPI interrupts
>> start from 64). In the above code, since irq_base would be 0 for
>> exynos4, the interrupt mapping is not working correctly. In your
>> previous version of the patch, you have given a option to the platform
>> code to choose the offset. Could that option be added to this series
>> also. Or a provision to use platform specific translate function
>> instead of the irq_domain_simple translator.
>>
>
> So I guess you have the A9 external nIRQ hooked up to another
> controller? Why can't the 0-31 interrupts get mapped to after the gic
> interrupts? Ultimately we want h/w irq numbers completely decoupled from
> linux irq numbers. So you will want to put that controller in devicetree
> and have an DT init function for it as well.

There are chained interrupt handlers mapped in between linux irq
number 0 to 31. So the offset for GIC interrupts was set to 32 (SGI[0]
= 32). The interrupt chaining for the interrupts mapped between 0 to
31 seems unnecessary though. I will try removing them and check.

>
> In anycase, there's a simple solution. You just need a call to
> irq_alloc_descs to reserve the first 32 interrupts before calling
> of_irq_init.
>
> Rob
>

Thanks for your comments.

Regards,
Thomas.
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