linux-kernel - Re: [PATCH V15 00/15] irqchip: Add LoongArch-related irqchip drivers

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Message-ID: <87fsiy53h3.wl-maz@kernel.org>
Date:   Mon, 18 Jul 2022 07:39:36 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Jianmin Lv <lvjianmin@...ngson.cn>
Cc:     Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, Hanjun Guo <guohanjun@...wei.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        Huacai Chen <chenhuacai@...ngson.cn>
Subject: Re: [PATCH V15 00/15] irqchip: Add LoongArch-related irqchip drivers

On Mon, 18 Jul 2022 02:07:21 +0100,
Jianmin Lv <lvjianmin@...ngson.cn> wrote:
> 
> 
> 
> On 2022/7/17 下午10:49, Marc Zyngier wrote:
> > On Sun, 17 Jul 2022 12:29:05 +0100,
> > Jianmin Lv <lvjianmin@...ngson.cn> wrote:
> >> 
> >> 
> >> 
> >> On 2022/7/17 下午6:02, Marc Zyngier wrote:
> >>> But the other issue is that you seem to call this function from two
> >>> different locations. This cannot be right, as there should be only one
> >>> probe order, and not multiple.
> >>> 
> >> 
> >> As we described two IRQ models(Legacy and Extended) in this cover
> >> letter, the parent domain of MSI domain can be htvec domain(Legacy) or
> >> eiointc domain(Extended). In MADT, only one APIC(HTPIC for htvec or
> >> EIOPIC for eiointc) is allowed to pass into kernel, and then in the
> >> irqchip driver, only one kind APIC of them can be parsed from MADT, so
> >> we have to support two probe order for them.
> > 
> > Do you really have the two variants in the wild? Or is this just
> > because this is a possibility?
> > 
> 
> Currently, there are not CPUs(used for PC and server) based on
> LoongArch shipped with only HTPIC, but with both HTPIC and EIOPIC, we
> just want to provide two choices for designers(but obviously, EIOPIC
> may be enough currently). Do you think we don't have to do like this,
> yes? If so, maybe we don't have to support ACPI-way entry for htvec
> currently, and do the work in future if required.

If the existing HW is only following the 'Extended' model, then I'd
suggest you only support this for now. It has two effects:

- it simplifies the current code, making it more maintainable and
  easier to reason about

- it sends the message to integrators that 'Extended' is the correct
  model, and that it is what they should support

Now, we don't have much time left to get this series into -next (I
will be closing the tree to new features this week, and only queue
fixes).

So whatever you need to do, please do it quickly so that we can have
at least some of this in 5.20.

Thanks,

	M.

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