linux-kernel - Re: [patch 07/16] genirq: Introduce helper irq_domain_set

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Date:	Fri, 14 Nov 2014 17:35:56 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	Yijing Wang <wangyijing@...wei.com>
Subject: Re: [patch 07/16] genirq: Introduce helper irq_domain_set_info()
 to reduce duplicated code

On 14/11/14 15:41, Jiang Liu wrote:
> On 2014/11/14 23:31, Marc Zyngier wrote:
>> On 12/11/14 13:43, Thomas Gleixner wrote:
>>> From: Jiang Liu <jiang.liu@...ux.intel.com>
>>>
>>> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
>>> Cc: Bjorn Helgaas <bhelgaas@...gle.com>
>>> Cc: Grant Likely <grant.likely@...aro.org>
>>> Cc: Marc Zyngier <marc.zyngier@....com>
>>> Cc: Yingjoe Chen <yingjoe.chen@...iatek.com>
>>> Cc: Yijing Wang <wangyijing@...wei.com>
>>> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
>>> ---
>>>  include/linux/irqdomain.h |    5 +++++
>>>  kernel/irq/irqdomain.c    |   10 ++++++++++
>>>  2 files changed, 15 insertions(+)
>>>
>>> Index: tip/include/linux/irqdomain.h
>>> ===================================================================
>>> --- tip.orig/include/linux/irqdomain.h
>>> +++ tip/include/linux/irqdomain.h
>>> @@ -33,6 +33,7 @@
>>>  #define _LINUX_IRQDOMAIN_H
>>>  
>>>  #include <linux/types.h>
>>> +#include <linux/irqhandler.h>
>>>  #include <linux/radix-tree.h>
>>>  
>>>  struct device_node;
>>> @@ -263,6 +264,10 @@ extern int irq_domain_set_hwirq_and_chip
>>>  					 irq_hw_number_t hwirq,
>>>  					 struct irq_chip *chip,
>>>  					 void *chip_data);
>>> +extern void irq_domain_set_info(struct irq_domain *domain, unsigned int virq,
>>> +				irq_hw_number_t hwirq, struct irq_chip *chip,
>>> +				void *chip_data, irq_flow_handler_t handler,
>>> +				void *handler_data, const char *handler_name);
>>>  extern void irq_domain_reset_irq_data(struct irq_data *irq_data);
>>>  extern void irq_domain_free_irqs_common(struct irq_domain *domain,
>>>  					int virq, int nr_irqs);
>>> Index: tip/kernel/irq/irqdomain.c
>>> ===================================================================
>>> --- tip.orig/kernel/irq/irqdomain.c
>>> +++ tip/kernel/irq/irqdomain.c
>>> @@ -882,6 +882,16 @@ int irq_domain_set_hwirq_and_chip(struct
>>>  	return 0;
>>>  }
>>>  
>>> +void irq_domain_set_info(struct irq_domain *domain, unsigned int virq,
>>> +			 irq_hw_number_t hwirq, struct irq_chip *chip,
>>> +			 void *chip_data, irq_flow_handler_t handler,
>>> +			 void *handler_data, const char *handler_name)
>>> +{
>>> +	irq_domain_set_hwirq_and_chip(domain, virq, hwirq, chip, chip_data);
>>> +	__irq_set_handler(virq, handler, 0, handler_name);
>>> +	irq_set_handler_data(virq, handler_data);
>>> +}
>>> +
>>
>> We still have the issue that, depending on where in the stack this is
>>  called, this will succeed or fail: If this is called from the inner
>> irqchip, __irq_set_handler() will fail, as it will look at the outer
>> domain as the (desc->irq_data.chip == &no_irq_chip) test fails (we
>> haven't set the top level yet).
>>
>> I have this very imperfect workaround in my tree:
>>
>> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
>> index d028b34..91e6515 100644
>> --- a/kernel/irq/chip.c
>> +++ b/kernel/irq/chip.c
>> @@ -731,7 +731,16 @@ __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
>>  	if (!handle) {
>>  		handle = handle_bad_irq;
>>  	} else {
>> -		if (WARN_ON(desc->irq_data.chip == &no_irq_chip))
>> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
>> +		struct irq_data *irq_data = &desc->irq_data;
>> +		while (irq_data) {
>> +			if (irq_data->chip != &no_irq_chip)
>> +				break;
>> +			irq_data = irq_data->parent_data;
>> +		}
>> +#endif
>> +
>> +		if (WARN_ON(!irq_data || irq_data->chip == &no_irq_chip))
>>  			goto out;
>>  	}
>>  
>> Which translate into: If there is at least one irqchip in the domain,
>> it will probably sort itself out. Not ideal. Any real solution to
>> this problem?
>>
>> GICv2 faces this exact problem, as some of its interrupts are used
>> directly, and some others are used through the MSI domain. In the
>> GIC driver, it is almost impossible to find out...
> Hi Marc,
> 	I prefer the above solution to relax the warning conditions.
> Changing the calling order in irq_domain_ops->alloc() looks a little
> strange, and other interrupt drivers may still run into the same issue.

OK. Where do we from from there? Do you want a proper patch, or will you
fold this into the existing code?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

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