linux-kernel - Re: [PATCH] irqchip: add keystone irq controller ip driver

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Date:	Mon, 21 Jul 2014 17:20:49 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Santosh Shilimkar <santosh.shilimkar@...com>,
	Jason Cooper <jason@...edaemon.net>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Rob Herring <robh+dt@...nel.org>,
	Kumar Gala <galak@...eaurora.org>, <ivan.khoronzhuk@...com>,
	<m-karicheri2@...com>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] irqchip: add keystone irq controller ip driver

Hi Jason,

On 07/18/2014 04:50 PM, Santosh Shilimkar wrote:
> On Friday 18 July 2014 08:59 AM, Jason Cooper wrote:
>> Grygorii,
>>
>> On Mon, Jul 14, 2014 at 06:27:57PM +0300, Grygorii Strashko wrote:
>>> On Keystone SOCs, DSP cores can send interrupts to ARM
>>> host using the IRQ controller IP. It provides 28 IRQ
>>> signals to ARM. The IRQ handler running on HOST OS can
>>> identify DSP signal source by analyzing SRCCx bits in
>>> IPCARx registers. This is one of the component used by
>>> the IPC mechanism used on Keystone SOCs.
>>>
>>> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
>>> ---
>>>   .../interrupt-controller/ti,keystone-irq.txt       |   36 +++
>>>   drivers/irqchip/Kconfig                            |    7 +
>>>   drivers/irqchip/Makefile                           |    1 +
>>>   drivers/irqchip/irq-keystone.c                     |  235 ++++++++++++++++++++
>>>   4 files changed, 279 insertions(+)
>>>   create mode 100644 Documentation/devicetree/bindings/interrupt-controller/ti,keystone-irq.txt
>>>   create mode 100644 drivers/irqchip/irq-keystone.c
>>>
> 
> 
> [..]
> 
>>> +
>>> +static const struct of_device_id keystone_irq_dt_ids[] = {
>>> +	{ .compatible = "ti,keystone-irq", },
>>> +	{},
>>> +};
>>> +MODULE_DEVICE_TABLE(of, keystone_irq_dt_ids);
>>> +
>>> +static struct platform_driver keystone_irq_device_driver = {
>>> +	.probe		= keystone_irq_probe,
>>> +	.remove		= keystone_irq_remove,
>>> +	.driver		= {
>>> +		.name	= "keystone_irq",
>>> +		.owner	= THIS_MODULE,
>>> +		.of_match_table	= of_match_ptr(keystone_irq_dt_ids),
>>> +	}
>>> +};
>>> +
>>> +module_platform_driver(keystone_irq_device_driver);
>>
>> My understanding of DSP use-cases is a little sparse, are there
>> legitimate scenarios where you might remove this driver during runtime?
>> Perhaps IRQCHIP_DECLARE() might be better?

IRQCHIP_DECLARE() isn't used here, because of two points:
- all consumers of this driver are initialized at module/driver_initcall time
  so, we don't need it to be initialized so early
- Keystone 2 supports DT-only boot and IRQ resolution APIs support probe
  deferring mechanism now, so we can solve properly any initialization dependencies
  if needed.

>>
> There is no scenario where driver needs to hotpluged out. Usecase is
> simple. Its really any other IRQCHIP. The difference is really the
> source of interrupts. Instead of peripherals interrupting the host
> OS9linux), here the DSP cores can send interrupts to Host OS.
> 
> Hope this clarifies.

Thanks for your review - I'll update and re-send.

Regards,
- grygorii
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