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

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Date:	Fri, 14 Nov 2014 23:41:21 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Marc Zyngier <marc.zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>
CC:	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 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.
Regards!
Gerry

> 
> Thanks,
> 
> 	M.
> 
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