linux-kernel - Re: [PATCH v3 1/6] irqchip: add support for Marvell Orion SoCs

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Message-ID: <51B72F5C.5020806@gmail.com>
Date:	Tue, 11 Jun 2013 16:08:28 +0200
From:	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Grant Likely <grant.likely@...aro.org>,
	Rob Herring <rob.herring@...xeda.com>,
	Rob Landley <rob@...dley.net>,
	John Stultz <john.stultz@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	devicetree-discuss@...ts.ozlabs.org, linux-doc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/6] irqchip: add support for Marvell Orion SoCs

On 06/11/13 15:45, Thomas Gleixner wrote:
> On Tue, 11 Jun 2013, Sebastian Hesselbarth wrote:
>> On 06/11/13 15:30, Thomas Gleixner wrote:
>>> On Tue, 11 Jun 2013, Thomas Gleixner wrote:
>>>> On Thu, 6 Jun 2013, Sebastian Hesselbarth wrote:
>>>>> This patch adds an irqchip driver for the main interrupt controller
>>>>> found
>>>>> on Marvell Orion SoCs (Kirkwood, Dove, Orion5x, Discovery Innovation).
>>>>> Corresponding device tree documentation is also added.
>>>>>
>>>>> Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
>>>>
>>>> Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
>>>
>>> Second thoughts:
>>>
>>>> +static void orion_bridge_irq_handler(unsigned int irq, struct irq_desc
>>>> *desc)
>>>> +{
>>>> +	struct irq_domain *d = irq_get_handler_data(irq);
>>>> +	struct irq_chip_generic *gc = irq_get_domain_generic_chip(d, irq);
>>>> +	u32 stat = readl_relaxed(gc->reg_base + ORION_BRIDGE_IRQ_CAUSE) &
>>>> +		gc->mask_cache;
>>>
>>> In init you map the first irq of that chip and install the chain
>>> handler for it. Now if that first irq fires, isn't that set in the
>>> cause register as well? And what acks that first irq?
>>
>> It is "acked" by acking all unmasked bridge irqs.
>
> Ok. A comment would be nice.
>
> But what about the bit in of that first irq in the cause register? If
> it's set on entry you call generic_handle_irq() for that as well. So
> if it's set you need to mask it in stat. If not, then it wants a
> comment.

I am not sure I can follow. orion_bridge_irq_init() maps the first
parent irq, i.e. hwirq 0 of orion_irq. The parent irq controller
clears that irq cause when all corresponding chained irqs are
cleared. The chained (bridge) irqs are cleared by
orion_bridge_irq_handler above.

I can put a note to the parent irqchip in orion_irq_init() that we
don't need to clear its cause register, if it is that what you mean?

Sebastian

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