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

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

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