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Date:	Sun, 09 Nov 2014 15:15:04 +0800
From:	Jiang Liu <jiang.liu@...ux.intel.com>
To:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	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>
CC:	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>,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [Patch Part2 v5 21/31] PCI/MSI: Enhance core to support hierarchy
 irqdomain

On 2014/11/9 12:26, Suravee Suthikulpanit wrote:
> Hi Gerry,
> 
> Please see my comments / questions below.
> 
> On 11/6/14 21:20, Jiang Liu wrote:
>> Enhance PCI MSI core to support hierarchy irqdomain, so the common
>> code could be shared among architectures.
>>
>> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
>> ---
>> Hi Thomas,
>>     These changes are a temporary solution, I'm working on another
>> patch set which will refine these interfaces, especially kill
>> arch_msi_irq_domain_{set|get}_hwirq().
>> Regards!
>> Gerry
> 
> Would the change includes the struct irqdomain_msi_data proposed by
> Thomas here (https://lkml.org/lkml/2014/11/6/210)?
Hi Suravee,
	I'm working on another patch set which will refine the way to
create irqdomain for MSI. I hope will solve all issues mentioned by
Thomas. I will post that patch set as RFC within one or two days.

> 
>> [...]
>> +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)
>> +        return ret;
>> +
> 
> When executing irq_domain_alloc_irqs_parent(), it triggers the following
> warning message due to
> 
>     WARN_ON(desc->irq_data.chip == &no_irq_chip)
> 
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 912 at kernel/irq/chip.c:734
> __irq_set_handler+0x138/0x13c()
> Modules linked in: mlx4_core(+) rtc_efi efivarfs
> CPU: 2 PID: 912 Comm: modprobe Not tainted 3.18.0-rc3-p2v5+ #53
> Call trace:
> [<fffffe00000963d4>] dump_backtrace+0x0/0x16c
> [<fffffe0000096550>] show_stack+0x10/0x1c
> [<fffffe000067545c>] dump_stack+0x74/0x98
> [<fffffe00000b205c>] warn_slowpath_common+0x84/0xac
> [<fffffe00000b2148>] warn_slowpath_null+0x14/0x20
> [<fffffe00000ed968>] __irq_set_handler+0x134/0x13c
> [<fffffe000042af14>] gic_irq_domain_map+0x4c/0xac
> [<fffffe000042afd4>] gic_irq_domain_alloc+0x60/0x88
> [<fffffe000042b374>] gicv2m_domain_alloc+0x30/0xa8
> [<fffffe00000efc1c>] __irq_domain_alloc_irqs+0x144/0x30c
> [<fffffe000042b58c>] gicv2m_setup_msi_irq+0xc0/0x118
> [<fffffe000044548c>] arch_setup_msi_irq+0x34/0x60
> [<fffffe0000445544>] arch_setup_msi_irqs+0x50/0xb0
> [<fffffe0000445e3c>] pci_enable_msix+0x310/0x39c
> [<fffffe0000445efc>] pci_enable_msix_range+0x34/0x9c
> ....
> 
> However, I think if we call irq_domain_set_hwirq_and_chip() in the
> msi_create_irq_domain() as suggested by Thomas, that should also fix
> this issue.
We didn't trigger this warning on x86 because only the outer-most
irqdomain will set irq flow handler. On ARM, the inner GIC domain
will set irq flow handler, but the irq_data->chip for outer-most
domain hasn't been set yet.

I'm still find a way out here. Maybe we need to relax the WARN_ON().

> 
>> +    for (i = 0; i < nr_irqs; i++) {
>> +        irq_domain_set_hwirq_and_chip(domain, virq + i, hwirq + i,
>> +                          domain->host_data,
>> +                          (void *)(long)i);
>> +        __irq_set_handler(virq + i, handle_edge_irq, 0, "edge");
>> +    }
> 
> Is there are a way to specify other type of handler besides edge?
Yes, the new patch set will address this requirement.

> 
>> [...]
>> +static void msi_domain_activate(struct irq_domain *domain,
>> +                struct irq_data *irq_data)
>> +{
>> +    struct msi_msg msg;
>> +
>> +    /*
>> +     * irq_data->chip_data is MSI/MSI-X offset.
>> +     * MSI-X message is written per-IRQ, the offset is always 0.
>> +     * MSI message denotes a contiguous group of IRQs, written for
>> 0th IRQ.
>> +     */
>> +    if (irq_data->chip_data)
>> +        return;
> 
> Actually, I am a bit confused with this comment here.  If you look at
> "/drivers/pci/msi.c: arch_setup_msi_irq()", it calls
> irq_set_chip_data(des->irq, chip) where chip is *msi_chip.
> 
> It looks like if the arch uses this API, it would conflict with what you
> have here where the irq_data->chip_data would be not NULL at the logic
> above, and would always return.
Good point, it's work on x86, but will break ARM or other platforms.
Will refine this part.
Regards!
Gerry
> 
> Thank you,
> 
> Suravee
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