linux-kernel - Re: [PATCH 2/3] irqchip: Add the Sophgo SG2042 MSI interrupt controller

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Message-ID:
 <MA0P287MB2822B7CFC338C7AED1F0A549FE5B2@MA0P287MB2822.INDP287.PROD.OUTLOOK.COM>
Date: Thu, 14 Nov 2024 08:20:24 +0800
From: Chen Wang <unicorn_wang@...look.com>
To: Thomas Gleixner <tglx@...utronix.de>, Chen Wang <unicornxw@...il.com>,
 u.kleine-koenig@...libre.com, aou@...s.berkeley.edu, arnd@...db.de,
 conor+dt@...nel.org, guoren@...nel.org, inochiama@...look.com,
 krzk+dt@...nel.org, palmer@...belt.com, paul.walmsley@...ive.com,
 robh@...nel.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-riscv@...ts.infradead.org, chao.wei@...hgo.com,
 xiaoguang.xing@...hgo.com, fengchun.li@...hgo.com
Subject: Re: [PATCH 2/3] irqchip: Add the Sophgo SG2042 MSI interrupt
 controller


On 2024/11/13 23:31, Thomas Gleixner wrote:
> On Wed, Nov 13 2024 at 14:43, Chen Wang wrote:
>> On 2024/11/13 14:14, Thomas Gleixner wrote:
>>>> +
>>>> +	middle_domain = irq_domain_create_hierarchy(plic_domain, 0, priv->num_irqs,
>>>> +						    fwnode,
>>>> +						    &pch_msi_middle_domain_ops,
>>>> +						    priv);
>>> So now you have created a domain. How is that supposed to be used by the
>>> PCI layer?
>> Here I create the domain and attached it to the fwnode. In PCI driver,
>> it can set this msi controller as its ""interrupt-parent" and find the
>> domain attached as below:
>>
>> static int pcie_probe(struct platform_device *pdev)
>> {
>>       struct device *dev = &pdev->dev;
>>       parent_node = of_irq_find_parent(dev->of_node);
>>       parent_domain = irq_find_host(parent_node);
>>       ...
>> }
> I assume you then want to create a global PCI/MSI domain via
> pci_msi_create_irq_domain(), right?
Yes, I am writing another pcie driver, which will call 
pci_msi_create_irq_domain() to create a child domain of this middle_domain.
>
> That's not the preferred way to do that. Any new implementation should
> use the MSI parent model, where each PCI device creates it's own per
> device MSI domain with the MSI interrupt controller as parent
> domain.
>
> There is a library with helper functions, irq-msi-lib.[ch]. See
> gicv2m_allocate_domains() or pch_msi_init_domains() for reference.

Thanks, I will check this out.

Regards,

Chen

>
> Thanks
>
>          tglx