Re: [PATCH v2 01/14] dt-bindings: remoteproc: Add TI PRUSS bindings

[Marc Zyngier <marc.zyngier@arm.com>]

On Thu, 14 Feb 2019 10:55:10 +0000,
Roger Quadros <rogerq@ti.com> wrote:
> 
> 
> On 14/02/19 10:37, Linus Walleij wrote:
> > On Thu, Feb 14, 2019 at 4:13 AM Suman Anna <s-anna@ti.com> wrote:
> >> [Me]
> > 
> >>> To be able to use hierarchical interrupt domain in the kernel, the top
> >>> interrupt controller must use the hierarchical (v2) irqdomain, so
> >>> if this is anything else than the ARM GIC it will be an interesting
> >>> undertaking to handle this.
> >>
> >> These are interrupt lines coming towards the host processor running
> >> Linux and are directly connected to the ARM GIC. This INTC module is
> >> actually an PRUSS internal interrupt controller that can take in 64 (on
> >> most SoCs) external events/interrupt sources and multiplexing them
> >> through two layers of many-to-one events-to-intr channels &
> >> intr-channels-to-host interrupts. Couple of the host interrupts go to
> >> the PRU cores themselves while the remaining ones come out of the IP to
> >> connect to other GICs in the SoC.
> > 
> > If the muxing is static (like set up once at probe) so that while
> > the system is running, there is one and one only event mapped to
> > the GIC from the component below it, then it is hierarchical.
> 
> This is how it looks.
> 
> [GIC]<---8---[INTC]<---64---[events from peripherals]
> 
> The 8 interrupt lines from INTC to the GIC are 1:1 mapped and fixed
> per SoC.  The muxing between 64 inputs to INTC and its 8 outputs are
> programmable and might not necessarily be static per boot/probe as
> it depends on what firmware is loaded on the PRU.

But the point is that at any given time, there are at most 8 out of 64
inputs that are used, right? You *never* end-up with two (or more) of
these "events" being multiplexed on a single output line.

If these assertions do hold, then your design is typical of a
hierarchy, for which we have countless examples in the tree (including
for some TI HW).

Thanks,
	M.

-- 
Jazz is not dead, it just smell funny.