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

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Message-ID: <20170116113804.GB23703@red-moon>
Date:   Mon, 16 Jan 2017 11:38:04 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Hanjun Guo <guohanjun@...wei.com>
Cc:     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>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        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 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.

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.

> Also devices connecting MBIgen may not consume all the interrupts produced
> by MBIgen, for example, MBIgen may produce 128 interrupts but only half of
> them are currently used, so _PRS here means "provide interrupt resources
> may consumed by devices connecting to it".

See above.

Lorenzo