linux-kernel - Re: [Patch Part2 v4 21/31] PCI/MSI: enhance PCI MSI core to support hierarchy irqdomain

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Message-ID: <545B5E5B.8090300@linux.intel.com>
Date:	Thu, 06 Nov 2014 19:41:15 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Grant Likely <grant.likely@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Yijing Wang <wangyijing@...wei.com>,
	Alexander Gordeev <agordeev@...hat.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Suravee Suthikulanit <suravee.suthikulpanit@....com>,
	x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
	LAK <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Patch Part2 v4 21/31] PCI/MSI: enhance PCI MSI core to support
 hierarchy irqdomain

On 2014/11/6 18:01, Thomas Gleixner wrote:
> On Tue, 4 Nov 2014, Jiang Liu wrote:
>> +#ifdef	CONFIG_PCI_MSI_IRQ_DOMAIN
>> +static inline irq_hw_number_t
>> +msi_get_hwirq(struct pci_dev *pdev, struct msi_desc *msidesc)
>> +{
>> +	return (irq_hw_number_t)msidesc->msi_attrib.entry_nr |
>> +		PCI_DEVID(pdev->bus->number, pdev->devfn) << 11 |
>> +		(pci_domain_nr(pdev->bus) & 0xFFFFFFFF) << 27;
>> +}
>> +
>> +static int msi_domain_alloc(struct irq_domain *domain, unsigned int virq,
>> +			    unsigned int nr_irqs, void *arg)
>> +{
>> +	int i, ret;
>> +	irq_hw_number_t hwirq = arch_msi_irq_domain_get_hwirq(arg);
>> +
>> +	if (irq_find_mapping(domain, hwirq) > 0)
>> +		return -EEXIST;
>> +
>> +	ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, arg);
>> +	if (ret >= 0)
>> +		for (i = 0; i < nr_irqs; i++) {
>> +			irq_domain_set_hwirq_and_chip(domain, virq + i,
>> +					hwirq + i, &msi_chip, (void *)(long)i);
> 
> I think msi_chip being a global unique thing is problematic. It does
> not allow multi platform kernels to select a chip at boot time and it
> does not allow per domain chip implementations when you have multiple
> msi domains. Aside of that msi_chip is a pretty bad name for a global.
> 
> The solution is rather simple and msi is wide spread enough to justify
> that.
> 
> struct irqdomain_msi_data {
>        struct irq_chip       *irq_chip;
> };
> 
> We make that a struct so we can accomodate for other special things
> which might be domain rather than architecture specific. One
> obvious use case would be to hold the arch_msi_irq_domain_get/set_hwirq
> callbacks.
> 
> struct irq_domain *msi_create_irq_domain(struct irq_domain *parent,
>        		  			 struct irqdomain_msi_data *data)
> {
>         struct irq_domain *domain;
> 
>         domain = irq_domain_add_tree(NULL, &msi_domain_ops, NULL);
>         if (domain) {
>                 domain->parent = parent;
> 		domain->msi_data = data;
> 	}
>         return domain;
> }
> 
> Now the above becomes:
> 
>     	struct irq_chip *msi_chip = domain->msi_data->irq_chip;
> 
> 	irq_domain_set_hwirq_and_chip(domain, virq + i,
> 				      hwirq + i, msi_chip, (void *)(long)i);
Hi Thomas,
	Actually I'm working on a patch set to improve MSI support in
the way you described above this afternoon. And I'm also trying to
split MSI code into PCI dependent part and PCI independent part.
I plan to add a file kernel/irq/msi.c to host PCI independent part,
is that OK? Or should I put it under something like drivers/msi/?
The PCI indepenent part will be used to support DMAR/HPET/HTIRQ and
some ARM/ARM64 interrupts.
Regards!
Gerry
> 
>> +int msi_irq_domain_alloc_irqs(struct irq_domain *domain, int type,
>> +			      struct pci_dev *dev, void *arg)
>> +{
>> +	int i, virq;
>> +	struct msi_desc *msidesc;
>> +	int node = dev_to_node(&dev->dev);
>> +
>> +	list_for_each_entry(msidesc, &dev->msi_list, list) {
>> +		arch_msi_irq_domain_set_hwirq(arg, msi_get_hwirq(dev, msidesc));
> 
> The arch_xxx callbacks want to be documented. It's not obvious what
> they are supposed to do.
> 
> Thanks,
> 
> 	tglx
> --
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