linux-kernel - Re: [RFC PATCH v0.2] PCI: Add support for tango PCIe host bridge

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Message-ID: <bc5bf8ad-69ef-4f14-f450-e162ddb5af7c@arm.com>
Date:   Wed, 12 Apr 2017 09:08:31 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Mason <slash.tmp@...e.fr>, Thomas Gleixner <tglx@...utronix.de>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Liviu Dudau <liviu.dudau@....com>,
        David Laight <david.laight@...lab.com>,
        linux-pci <linux-pci@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Thibaud Cornic <thibaud_cornic@...madesigns.com>,
        Phuong Nguyen <phuong_nguyen@...madesigns.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH v0.2] PCI: Add support for tango PCIe host bridge

On 11/04/17 18:52, Mason wrote:
> On 11/04/2017 18:43, Marc Zyngier wrote:
> 
>> On 11/04/17 17:26, Mason wrote:
>>
>>> Is there a function to map virq to the hwirq in any domain?
>>
>> Be more precise. If you want the hwirq associated with the view of a
>> virq in a given domain, that's the hwirq field in the corresponding
>> irq_data structure. Or are you after something else?
> 
> I registered an unmask method for my irq_chip.
> (IIUC, I'm supposed to unmask a specific MSI in this callback.)
> 
> # cat /proc/interrupts 
>            CPU0       CPU1       
>  30:          0          0    MSIfoo      0 Edge      aerdrv
>  34:          0          0    MSIfoo 524288 Edge      xhci_hcd
>  35:          0          0    MSIfoo 524289 Edge      xhci_hcd
>  36:          0          0    MSIfoo 524290 Edge      xhci_hcd
> 
> 
> void foo_unmask(struct irq_data *data)
> {
> 	int xx,yy;
> 	struct irq_domain *dom = data->domain;
> 	printk("%s: irq_data=%p irq=%u hwirq=%lu chip=%p dom=%p pdata=%p data=%p\n",
> 		__func__, data, data->irq, data->hwirq, data->chip, data->domain,
> 		data->parent_data, data->chip_data);
> 	printk("%s ops=%p data=%p parent=%p\n\n",
> 		dom->name, dom->ops, dom->host_data, dom->parent);
> 	printk("pcie=%p\n", dom->parent->host_data);
> 	//dump_stack();
> 	pci_msi_unmask_irq(data);
> 	struct tango_pcie *pcie = data->domain->parent->host_data;
> 	printk("\n%s: pcie=%p irq=%u hwirq=%lu\n\n",
> 		__func__, pcie, data->irq, data->hwirq);
> 	xx = irq_find_mapping(pcie->irq_domain, data->hwirq);
> 	yy = irq_find_mapping(pcie->msi_domain, data->hwirq);

Do you realize that hwirq is *per domain*, and only makes sense to *one*
irqchip? What you've written here doesn't make any sense.

> 	printk("xx=%d yy=%d\n", xx, yy);
> }
> 
> so data->irq is the virq (30, 34, 35, 36)
> and data->hwirq is the domain hwirq (0, 524288, 524289, 524290)
> 
> Is there a way to map hwirq 524288 to MSI 0, hwirq 524289 to MSI 1, etc?

Why would you need to do such a thing?
- In MSI domain: IRQ34 -> hwirq 524288
- In foo domain: IRQ34 -> hwirq [whatever your driver has allocated]

The data is already there, at your fingertips. Just deal with with your
"foo" irqchip.

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