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

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Date:	Thu, 6 Nov 2014 11:30:47 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Jiang Liu <jiang.liu@...ux.intel.com>
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 Thu, 6 Nov 2014, 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.

That needs to hand in the domain as an argument as well.

Thanks,

	tglx
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