From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hanjun Guo <hanjun.guo@linaro.org>
Subject: Re: [PATCH v7 13/17] ARM64 / ACPI: Add GICv2 specific ACPI boot support
Date: Fri, 23 Jan 2015 17:38:26 +0800
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To: Marc Zyngier <marc.zyngier@arm.com>, "grant.likely@linaro.org" <grant.likely@linaro.org>
Cc: Catalin Marinas <Catalin.Marinas@arm.com>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Olof Johansson <olof@lixom.net>, Arnd Bergmann <arnd@arndb.de>, Mark Rutland <Mark.Rutland@arm.com>, Will Deacon <Will.Deacon@arm.com>, Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com>, "graeme.gregory@linaro.org" <graeme.gregory@linaro.org>, Sudeep Holla <Sudeep.Holla@arm.com>, "jcm@redhat.com" <jcm@redhat.com>, Jason Cooper <jason@lakedaemon.net>, Bjorn Helgaas <bhelgaas@google.com>, Mark Brown <broonie@kernel.org>, Rob Herring <robh@kernel.org>, Robert Richter <rric@kernel.org>, Randy Dunlap <rdunlap@infradead.org>, Charles Garcia-Tobin <Charles.Garcia-Tobin@arm.com>, "phoenix.liyi@huawei.com" <phoenix.liyi@huawei.com>, Timur Tabi <timur@codeaurora.org>, "suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>, "wangyijing@huawei.com" <wangyijing@huawei.com>, linux-acpi@vger
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On 2015=E5=B9=B401=E6=9C=8822=E6=97=A5 22:46, Marc Zyngier wrote:
> Hi Hanjun,
>
> On 22/01/15 12:46, Hanjun Guo wrote:
>> Hi Marc,
>>
>> We (Tomasz, Suravee and me) are working on supporting stacked domain=
 on
>> ACPI, and rework GIC ACPI related patch, before we going further, we
>> need your guidance to see if we are going the right direction.
>>
>>     - You said that we spread GIC related code every where, so how
>>       about put all the ACPI related GIC init code in one file under
>>       drivers/irqchip/ with name irq-gic-acpi.c?
>
> That would certainly be an improvement.
>
>>     - ACPI only support one GICD for now, so we assume that there
>>      only one gicv2/v3 core domain and every device not using MSI
>>       will refer to that irqdomain in default.
>
> That's good enough, provided that nobody comes up with any form of
> chained interrupt controller (in whatever way that's implemented). AC=
PI
> doesn't seem to cater for that anyway.
>
> But default domains are only a quick optimization (it is only there t=
o
> cope with code that didn't know about irq domains at all). What we ne=
ed
> is a proper integration of the ACPI namespace in the irq domain code.
> Being able to lookup a domain by ACPI table, for example (just like
> irq_find_host returns the domain associated to a DT node).

I totally agree, so we have different ways to handle devices using
MSI and devices not using MSI.

   - Devices using MSI, there is a IORT table to map the dev id to ITS,
     then every device can easily lookup a domain;

   - Devices not using MSI, we only present the GSI (hwirq num) used
     in DSDT by this device to OS, no property to indicate its interrup=
t
     parent, since we have only one domain for now, we can just let
     those devices refer to the gic core domain, and it will work.

=46or x86, devices using GSI have no such problem, because every
IOAPIC have the GSI base reported and how many GSI is supported,
so with a GSI num, we can easily find a IOAPIC then pointing to
its irqdomain, can we do something similar to x86 here?

>
> This would ensure that we can reuse most of the existing code (stacke=
d
> domains, per-device MSI domains [WIP]) without too much effort.

I agree.

Thanks
Hanjun