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 10:14:11 -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 10:09 AM, Marc Zyngier wrote:
> On 16/07/15 17:50, David Daney wrote:
[...]
>>> 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);
>
> Neither.
>
> The way to do it is to make this a *separate* IRQ domain stacked onto
> the SPI domain. No funky hook on the side. If it doesn't go through the
> normal kernel API, it doesn't reach the GIC.

Yes, the irqdomain does handle mapping SPI -> irq, and the message can 
be derived from the SPI.  However, the irqdomain infrastructure cannot 
supply values for either assert_addr or deassert_addr.

Those are needed in order to use SPI.  How would you suggest that they 
be obtained?


David Daney


>
> 	M.
>

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