linux-kernel - Re: [PATCH v5 1/3] initialize each mbigen device node as a interrupt controller.

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Message-ID: <alpine.DEB.2.11.1510130842070.6097@nanos>
Date:	Tue, 13 Oct 2015 08:55:35 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"majun (F)" <majun258@...wei.com>
cc:	Marc Zyngier <marc.zyngier@....com>, Catalin.Marinas@....com,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Will.Deacon@....com, mark.rutland@....com, jason@...edaemon.net,
	lizefan@...wei.com, huxinwei@...wei.com, dingtianhong@...wei.com,
	zhaojunhua@...ilicon.com, liguozhu@...ilicon.com,
	xuwei5@...ilicon.com, wei.chenwei@...ilicon.com,
	guohanjun@...wei.com, wuyun.wu@...wei.com, guodong.xu@...aro.org,
	haojian.zhuang@...aro.org, zhangfei.gao@...aro.org,
	usman.ahmad@...aro.org, klimov.linux@...il.com
Subject: Re: [PATCH v5 1/3] initialize each mbigen device node as a interrupt
 controller.

Majun,

On Tue, 13 Oct 2015, majun (F) wrote:
> 在 2015/10/12 0:45, Thomas Gleixner 写道:
> > So now in the mbigen case this looks like this:
> > 
> >     [MSI-BUS] ----- [MBIGEN]<-------------------[Device interrupt]
> > 
> > Again, you have a 'wire' from the device to the MSI unit (MBIGEN) and
> > we do not care about that 'wire' either. What we care about is how we
> > find the MSI (mbigen) configuration registers for a particular
> > device. So we need a DT/ACPI entry which describes those configuration
> > registers and whatever supplementary information is required. That
> > will make the mbigen driver extremly simple.
> > 
> 
> According to your suggestions, I tried to make the hardware structure likes below:
> 
> device(8250 uart) -> mbigne -> ITS-pMSI --> ITS --> GIC

I'm not sure whether mbigen should be connected to ITS-pMSI (I assume
you mean ITS-PCI-MSI).

mbigen is a seperate MSI domain, so it should connect to ITS, but I
leave that to Marc.
 
> And  8250 uart dts node is:
> 
>  8250_uart {
> 	compatible = "xxx";
> 	msi-parent = < &mbigen>;
> 	config_addr = <xxxxx> ; /* configuration register */
> 	interrupts = <x>;
> 	interrupt-parent = ?
> }
> 
> My question is what's the interrupt-parent should be?

There is no interrupt parent for 8250_uart. Why would you want that?
I'm really not a DT expert, but I think you want something like this:

  8250_uart {
 	compatible = "xxx";
 	msi-parent = < &mbigen_node5>;
 	interrupt-map = <&mbigen5 0>;
  };

and then have

  mbigen_node5 {
  	...
	reg = <....>;
  };

So the other devices which are connected to mbigen_node5 have the same
msi-parent. But then again, please discuss that with Marc and the DT
wizards.

Thanks,

	tglx