Re: [Xen-devel] [GSoC-2019] About the crossbar and xen

[Hunyue Yau <hy-gsoc@xxxxxxxxxxxxxxx>]

Denis,

Not sure if you gone through this - the interrupt routing is described in the 
TRM chapter on interrupt controllers. In my edition (large file, don't want to 
redownload unless needed.), this is chapter 17. Table 17-2 (in my edition)  
should address a lot of what you are asking. It shows the IRQ Input line (aka 
GIC ID number), the IRQ cross bar instance along with the config register and 
some description. Figure 17-1 shows the the layout. 

From what I can tell, the cross bar is so the interrupt can be sent to the 
other processor on the die besides the cortex-a (aka MPU in the TRM). Mapping 
the TRM names to DT names might still be bit of work but this should give you 
an idea what to look for in the Linux kernel to backout the names used.


On Wednesday, July 10, 2019 22:43:37 Denis Obrezkov wrote:
> Hi,
> 
> On 7/10/19 10:17 PM, Stefano Stabellini wrote:
> > On Wed, 10 Jul 2019, Denis Obrezkov wrote:
> >> Hi,
> >> 
> >> On 7/10/19 9:49 PM, Stefano Stabellini wrote:
> >>>   phandle = <0x00000002>;
> >>> 
> >>> I think that means that interrupts go to the GIC via Crossbar; i.e. the
> >>> parent interrupt controller of Crossbar is the GIC.
> >> 
> >> But the crossbar's interrupt-parent node is 0x00000008 and phandle value
> >> 0x00000008 belongs to
> >> interrupt-controller@48281000 {
> >> 
> >>            compatible = "ti,omap5-wugen-mpu", "ti,omap4-wugen-mpu";
> >> 
> >> For me it looks like interrupts from crossbar goes to wugen and the from
> >> wugen to GIC. But I don't quite understand it.
> > 
> > Hi Denis,
> > 
> > I only read your email and got a partial picture. I read the full device
> > tree now and the hierarchy is as follow:
> > 
> > - crossbar routes to phandle 8
> > - phandle 8 is omap5-wugen-mpu and routes to phandle 2
> > - phandle 2 is the GIC
> > 
> > So:
> > 
> > crossbar -> omap5-wugen-mpu -> GIC
> 
> I am interested whether we should do something with omap5-wugen-mpu. I
> found that crossbar is connected to GIC. And on some schemes in trm it
> is connected via omap5-wugen-mpu. So, it is not clear for me whether it
> should be handled in xen.

-- 
Hunyue Yau
http://www.hy-research.com/

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