linux-kernel - Re: [PATCH v7 15/15] irqchip: mbigen: Add ACPI support

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Message-ID: <587E072F.3020305@huawei.com>
Date:   Tue, 17 Jan 2017 19:59:43 +0800
From:   Hanjun Guo <guohanjun@...wei.com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Hanjun Guo <hanjun.guo@...aro.org>, <huxinwei@...wei.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>, <yimin@...wei.com>,
        Jon Masters <jcm@...hat.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Greg KH <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>,
        Sinan Kaya <okaya@...eaurora.org>,
        <linux-acpi@...r.kernel.org>,
        Xinwei Kong <kong.kongxinwei@...ilicon.com>,
        Matthias Brugger <mbrugger@...e.com>,
        Tomasz Nowicki <tn@...ihalf.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Agustin Vega-Frias <agustinv@...eaurora.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        Ma Jun <majun258@...wei.com>
Subject: Re: [PATCH v7 15/15] irqchip: mbigen: Add ACPI support

On 2017/1/16 23:24, Lorenzo Pieralisi wrote:
> On Mon, Jan 16, 2017 at 10:23:16PM +0800, Hanjun Guo wrote:
>> Hi Lorenzo,
>>
>> On 2017/1/16 19:38, Lorenzo Pieralisi wrote:
>>> On Sat, Jan 14, 2017 at 10:56:54AM +0800, Hanjun Guo wrote:
>>>> Hi Lorenzo,
>>>>
>>>> On 2017/1/13 18:21, Lorenzo Pieralisi wrote:
>>>>> On Wed, Jan 11, 2017 at 11:06:39PM +0800, Hanjun Guo wrote:
>>>>>> With the preparation of platform msi support and interrupt producer
>>>>>> in DSDT, we can add mbigen ACPI support now.
>>>>>>
>>>>>> We are using _PRS methd to indicate number of irq pins instead
>>>>>> of num_pins in DT to avoid _DSD usage in this case.
>>>>>>
>>>>>> For mbi-gen,
>>>>>>     Device(MBI0) {
>>>>>>           Name(_HID, "HISI0152")
>>>>>>           Name(_UID, Zero)
>>>>>>           Name(_CRS, ResourceTemplate() {
>>>>>>                   Memory32Fixed(ReadWrite, 0xa0080000, 0x10000)
>>>>>>           })
>>>>>>
>>>>>>           Name (_PRS, ResourceTemplate() {
>>>>>> 		  Interrupt(ResourceProducer,...) {12,14,....}
>>>>> I still do not understand why you are using _PRS for this, I think
>>>>> the MBIgen configuration is static and if it is so the Interrupt
>>>>> resource should be part of the _CRS unless there is something I am
>>>>> missing here.
>>>> Sorry for not clear in the commit message. MBIgen is an interrupt producer
>>>> which produces irq resource to devices connecting to it, and MBIgen itself
>>>> don't consume wired interrupts.
>>> That's why you mark it as ResourceProducer, but that's not a reason to
>>> put it in the _PRS instead of _CRS.
>> If using _CRS for the interrupt resource, the irq number represented
>> will be mapped (i.e acpi_register_gsi()), then will conflict with the
>> irq number of devices consuming it (mbigen is producing the
>> interrupts), but I agree with you that let's ask Rafael's point of
>> view.
> Aha ! So here is why you are using _PRS because the kernel turns _CRS
> Interrupt resources (even producers) into GSIs which is probably a
> kernel bug, is that the reason ?

I thought _CRS is for devices consuming resources, it's a kind of misunderstanding.

>
> We don't abuse firmware bindings to make the kernel work, that's _never_
> a good idea.
>
> If the interrupt resource is a Resource Producer core ACPI should not
> register the IRQ because that's not a GSI, probably this should be part of
> Agustin changes too ?

Agreed. If it's a Resource Producer,
- it's not a GSI
- and it should not be mapped to any irq domains

I think Agustin needs to add the changes to the patch set but only for
CONFIG_ACPI_GENERIC_GSI=y, not bother the core code as the complex
history of firmware in x86, what do you think?

>
>>> IIUC _PRS is there to provide a way to define the possible resource
>>> settings of a _configurable_ device (ie programmable) so that the actual
>>> resource value you would programme with a call to its _SRS is sane (ie
>>> the OS has a way, through the _PRS, to detect what possible resource
>>> settings are available for the device).
>>>
>>> I think Rafael has more insights into how the _PRS is used on x86
>>> systems so I would ask his point of view here before merrily merging
>>> this code.
>> OK, Rafael is traveling now, hope he will have time to take a look.
>>
>> How about updating this patch set then sending a new version for review
>> with this patch unchanged? if Rafael have comments on this one, I will
>> send a single updated one for this patch (if no other changes).
> I think this patch (and the FW that goes with it) is wrong, but the rest
> of the series, in particular the IORT bits, are ok with me.

Thanks, I updated the patch using _CRS and firmware, with minor changes for
Agustin's patch set, mbigen works pretty good as before.

I will comment on Agustin's patch set.

Thanks
Hanjun