lkml.org 
[lkml]   [2014]   [Nov]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [V10 PATCH 2/2] irqchip: gicv2m: Add supports for ARM GICv2m MSI(-X)


On 11/4/14 04:06, Thomas Gleixner wrote:
> On Mon, 3 Nov 2014, Suravee Suthikulanit wrote:
>> On 11/3/2014 4:51 PM, Thomas Gleixner wrote:
>>> On Mon, 3 Nov 2014, suravee.suthikulpanit@amd.com wrote:
>>>> + irq_domain_set_hwirq_and_chip(v2m->domain, virq, hwirq,
>>>> + &v2m_chip, v2m);
>>>> +
>>>> + irq_set_msi_desc(hwirq, desc);
>>>> + irq_set_irq_type(hwirq, IRQ_TYPE_EDGE_RISING);
>>>
>>> Sure both calls work perfectly fine as long as virq == hwirq, right?
>>
>> I was running into an issue when calling the irq_domain_alloc_irq_parent(), it
>> requires of_phandle_args pointer to be passed in. However, this does not work
>> for GICv2m since it does not have interrupt information in the device tree.
>> So, I decided at first to use direct (virq == hwirq) mapping, which simplifies
>> the code a bit, but might not be ideal solution, as you pointed out.
>
> It's not only far from ideal. It's not a solution at all. Simply
> because there is no guarantee for virq == hwirq.
>
>> An alternative would be to create a temporary struct of_phandle_args, and
>> populate it with the interrupt information for the requested MSI. Then pass it
>> to:
>> --> irq_domain_alloc_irq_parent
>> |--> gic_irq_domain_alloc
>> |--> gic_irq_domain_xlate
>> |--> gic_irq_domain_map
>>
>> However, this would still not be ideal if we want to support ACPI. Another
>
> Neither device tree nor ACPI has anything to do with MSI interrupts at
> runtime.
>
> All they do is to tell that there is a MSI controller and where the
> registers are and in the worst case fixups for a borked MSI_TYPER
> register.
>
> So either the TYPER reg or DT/ACPI gives you a fixed hwirq range which
> is reserved for MSI. And that's all you need, right?
>
Right, I get that part. Figuring out the fixed hwirq range for MSI is
not the point I am trying to make here.

> [...]
> All you need is to pick one hwirq out of the existing fixed range and
> associate it to a newly allocated virq. That's the only information
> the underlying gic domain has to know about, because it needs to
> translate from the hwirq to the virq in the low level entry handler
> gic_handle_irq().

And that's what I am trying to do here except that GIC is expecting that
information to be passed to it via irq_domain_alloc_irqs(..., args)
where args is struct of_phandle_args (e.g. in the kernel/irqdomain.c:
irq_create_of_mapping). This works fine when specifying interrupt from
DT, but that is not always the case.

Currently, I can just create a fake of_phandle_args just to pass the
hwirq information to GIC.

--> gicv2m_setup_msi_irq()
| struct of_phandle_args phan;
| phan.np = NULL;
| phan.args_count = 3;
| phan.args[0] = 0;
| phan.args[1] = hwirq - 32;
| phan.args[2] = IRQ_TYPE_EDGE_RISING;
|--> irq_domain_alloc_irqs(d, 1, NUMA_NO_NODE, &phan);
|--> gicv2m_domain_alloc(d, virq, nr_irqs, arg)
|--> irq_domain_alloc_irqs_parent(d, virq, nr_irqs, arg);

I am trying to figure out what would be a common data structure for this
purpose that would work for both Dt and non-DT case (e.g. GICv2m MSI).
Unless you think this is ok.

Thanks,
Suravee


\
 
 \ /
  Last update: 2014-11-04 15:41    [W:0.072 / U:1.032 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site