linux-kernel - Re: [V10 PATCH 2/2] irqchip: gicv2m: Add supports for ARM GICv2m MSI(-X)

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Date:	Wed, 5 Nov 2014 18:05:32 -0600
From:	Suravee Suthikulanit <suravee.suthikulpanit@....com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>, <marc.zyngier@....com>,
	<mark.rutland@....com>, <jason@...edaemon.net>,
	<tglx@...utronix.de>
CC:	<Catalin.Marinas@....com>, <Will.Deacon@....com>,
	<liviu.dudau@....com>, <Harish.Kasiviswanathan@....com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [V10 PATCH 2/2] irqchip: gicv2m: Add supports for ARM GICv2m
 MSI(-X)

On 11/4/2014 7:01 AM, Jiang Liu wrote:
> Hi Suravee,
> 	You may build a two level hierarchy irqdomains. Use the
> utilities in this thread
> http://www.spinics.net/lists/arm-kernel/msg374722.html  to build an MSI
> irqdomain to manage MSI controllers
> in PCI devices. And build another irqdomain to manage SPI allocation
> in GICv2.
> 	That is: MSI irqdomain (program MSI registers)  -->
> GIV irqdomain (manage SPIs in GICv2 controller)
>
> Regards!
> Gerry

Gerry,

I try out your patch from the link above, and I have a couple 
questions/issues.

1. In the drivers/pci/msi.c: msi_irq_domain_alloc_irqs(), it seems that 
the hwirq comes from msi_get_hwirq(dev, msidesc). In GICv2m, hwirq for 
MSI is fixed over a specific range. This might require arch-specific
callback.

2. In msi_domain_activate, why "if (!irq_data->chip_data)"?

3. In, msi_domain_alloc():

- There should be a way to specify other types of irq handler besides 
the "handle_edge_irq". In case of GIC, it needs handle_fasteoi_irq.

- When calling irq_domain_set_hwirq_and_chip(), you are passing "(void 
*)(long)i" for the "void *chip_data" parameter. What is this used for, 
and where?  Shouldn't this be pointing to arch-specific data structure?

- The code is calling irq_domain_alloc_irqs_parent before the loop, 
which calls irq_domain_set_hwirq_and_chip() and __irq_set_handler. 
Shouldn't the order be switched?

- Overall, it seems that msi_domain_alloc() could be quite different 
across architectures. Would it be possible to declare this function as 
weak, and allow arch to override (similar to arch_setup_msi_irq)?

Thanks,

Suravee

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