linux-kernel - Re: [PATCH V4 1/4] ACPI / PCI: fix LPIC IRQ model default PCI IRQ polarity

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Date:   Fri, 21 Oct 2022 07:01:29 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Jianmin Lv <lvjianmin@...ngson.cn>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>, linux-kernel@...r.kernel.org,
        loongarch@...ts.linux.dev, Jiaxun Yang <jiaxun.yang@...goat.com>,
        Huacai Chen <chenhuacai@...ngson.cn>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Len Brown <lenb@...nel.org>, rafael@...nel.org,
        linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH V4 1/4] ACPI / PCI: fix LPIC IRQ model default PCI IRQ
 polarity

On Fri, Oct 21, 2022 at 09:58:57AM +0800, Jianmin Lv wrote:
> On 2022/10/21 上午12:47, Bjorn Helgaas wrote:
> > On Thu, Oct 20, 2022 at 04:22:02PM +0800, Jianmin Lv wrote:
> > > On LoongArch ACPI based systems, the PCI devices (e.g. sata
> > > controlers and PCI-to-to PCI bridge controlers) existed in
> > > Loongson chipsets output high-level interrupt signal to the
> > > interrupt controller they connected to,

> > The point is that one should be able to write this code from a spec,
> > without having to empirically discover the interrupt polarity.  What
> > spec tells you about using ACTIVE_HIGH here?
> > 
> Yes, no mentions for the inverter in ACPI spec, the description about
> device interrupt type can be found in Loongson chipset manual:
> 
> https://github.com/loongson/LoongArch-Documentation/blob/main/docs/Loongson-7A1000-usermanual-EN/interrupt-controller/device-interrupt-types.adoc

That's the kind of reference I was looking for.  The link to HTML is
convenient in some ways, but since specs evolve over time and URLs are
ephemeral, I think a citation like "Loongson 7A1000 Bridge User Manual
v2.00, sec 5.3" is more likely to be useful far in the future.

Bjorn