linux-kernel - Re: [PATCH RFC V2 02/10] irqchip: Add LoongArch CPU interrupt controller support

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Date:   Tue, 07 Jun 2022 07:56:52 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Jianmin Lv <lvjianmin@...ngson.cn>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Huacai Chen <chenhuacai@...il.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Hanjun Guo <guohanjun@...wei.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH RFC V2 02/10] irqchip: Add LoongArch CPU interrupt controller support

On Tue, 07 Jun 2022 04:41:22 +0100,
Jianmin Lv <lvjianmin@...ngson.cn> wrote:
> 
> 
> On 2022/6/6 下午6:02, Marc Zyngier wrote:
> > + Lorenzo and Hanjun who maintain the ACPI irq code
> > 
> > On Thu, 02 Jun 2022 04:16:30 +0100,
> > Jianmin Lv <lvjianmin@...ngson.cn> wrote:

[...]

> >> I'm so sorry, I really don't find a way to reuse driver/acpi/irq.c
> >> after my humble work.
> > I don't think reimplementing ACPI is the solution. What could be a
> > reasonable approach is a way to overload the retrieval of the
> > acpi_gsi_domain_id fwnode with a GSI parameter.
> > 
> > I hacked the following patch, which will give you an idea of what I
> > have in mind (only compile-tested).
> 
> 
> Hi, Marc, thanks so much for your patch. I have verified it on my
> LoongArch machine and it works well.
> 
> 
> BTW, in acpi_get_irq_source_fwhandle(), maybe
> acpi_get_gsi_domain_id(ctx->index) is needed to changed to
> acpi_get_gsi_domain_id(irq->interrupts[ctx->index])?

Yes, absolutely. Thanks for spotting it.

> I have another question, for LoongArch, acpi_isa_irq_to_gsi is
> required to implemente, but no common version, do we need to
> implemente an weak version in driver/acpi/irq.c as following?
> 
> 
> int __weak acpi_isa_irq_to_gsi(unsigned int isa_irq, u32 *gsi)
> {
>         if (gsi)
>                 *gsi = isa_irq;
>         return 0;
> }

Do you actually have CONFIG_ISA? In 2022? For a brand new architecture?

If you really have to, then this needs to be a bit more involved:

#ifdef CONFIG_ISA
int __weak acpi_isa_irq_to_gsi(unsigned int isa_irq, u32 *gsi)
{
	if (irq < nr_legacy_irqs()) {
		*gsi = isa_irq;
		return 0;
	}

	return -1;
}
#endif

But I'd rather you get rid of any such legacy if this can be avoided.

> I'll use the way you provided here to reuse driver/acpi/irq.c in next
> version. How should I do next? Should I integrate your patch into my
> next version or wait for you to merge it first?

Please pick up the patch (with the above fix), and use it as a prefix
to your series. It needs to be reviewed by the relevant maintainers
anyway.

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.