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

[Jiang Liu <jiang.liu@linux.intel.com>]

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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