linux-kernel - Re: [PATCH 4/5] irqchip: gic-v3: Add gic_get_irq_domain() to get the irqdomain of the GIC.

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Date:	Thu, 16 Jul 2015 09:50:10 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Marc Zyngier <marc.zyngier@....com>
CC:	David Daney <ddaney.cavm@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	Robert Richter <rrichter@...ium.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 4/5] irqchip: gic-v3: Add gic_get_irq_domain() to get
 the irqdomain of the GIC.

On 07/16/2015 12:38 AM, Marc Zyngier wrote:
> On 15/07/15 19:57, David Daney wrote:
>> On 07/15/2015 10:12 AM, Marc Zyngier wrote:
>>> On 15/07/15 17:54, David Daney wrote:
>>>> From: David Daney <david.daney@...ium.com>
>>>>
>>>> Needed to map SPI interrupt sources.
>>>>
>>>> Signed-off-by: David Daney <david.daney@...ium.com>
>>>> ---
>>>>    drivers/irqchip/irq-gic-v3.c       | 5 +++++
>>>>    include/linux/irqchip/arm-gic-v3.h | 1 +
>>>>    2 files changed, 6 insertions(+)
>>>>
>>>> diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
>>>> index c52f7ba..0019fed 100644
>>>> --- a/drivers/irqchip/irq-gic-v3.c
>>>> +++ b/drivers/irqchip/irq-gic-v3.c
>>>> @@ -58,6 +58,11 @@ static struct gic_chip_data gic_data __read_mostly;
>>>>    /* Our default, arbitrary priority value. Linux only uses one anyway. */
>>>>    #define DEFAULT_PMR_VALUE	0xf0
>>>>
>>>> +struct irq_domain *gic_get_irq_domain(void)
>>>> +{
>>>> +	return gic_data.domain;
>>>> +}
>>>> +
>>>>    static inline unsigned int gic_irq(struct irq_data *d)
>>>>    {
>>>>    	return d->hwirq;
>>>> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h
>>>> index 18e3757..5992224 100644
>>>> --- a/include/linux/irqchip/arm-gic-v3.h
>>>> +++ b/include/linux/irqchip/arm-gic-v3.h
>>>> @@ -391,6 +391,7 @@ int its_init(struct device_node *node, struct rdists *rdists,
>>>>
>>>>    typedef u32 (*its_pci_requester_id_t)(struct pci_dev *, u16);
>>>>    void set_its_pci_requester_id(its_pci_requester_id_t fn);
>>>> +struct irq_domain *gic_get_irq_domain(void);
>>>>    #endif
[...]
>
>> We need a way to be able to map these.
>
> However you're going to map them, it will not be by just blindly
> exporting random irqdomains from an unsuspecting interrupt controller.

There is nothing random about it.  The ARM architects specified that 
there is exactly One True GIC in a system.  If we need to do something 
with the GIC, it is not a "random ... unsuspecting interrupt 
controller", it is *The* GIC.

>
> Patch 5 has established that you're using "virtual wire" SPIs, so we
> need to work on exposing that with the normal kernel abstraction, and
> not by messing with the internals of the GIC.
>

Agreed.

The MSI system has pci_enable_msix()/pci_disable_msix().

I would propose something like:

struct gic_spi_entry {
	int spi   /* SPI number */
	int irq;  /* kernel irq number mapped to the spi*/
	u32 msg;  /* message to be written */
	u64 assert_addr;
	u64 deassert_addr;
};

/* Fill in the SPI processing information */
int gic_map_spi(int spi, struct gic_spi_entry *data);

David Daney



> Thanks,
>
> 	M.
>

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