Re: [EXT] Re: [PATCH v9 2/4] irqchip: Add IMX MU MSI controller driver

Marc Zyngier
2022-09-10T14:40:32Z

On Fri, 09 Sep 2022 15:52:45 +0100,
Frank Li <frank.li@nxp.com> wrote:
>
> > > + select IRQ_DOMAIN
> > > + select IRQ_DOMAIN_HIERARCHY
> > > + select GENERIC_MSI_IRQ_DOMAIN
> > > + help
> > > + MU work as MSI controller to do general doorbell
> >
> > I'm not sure this is that generic. It really is limited to CPU-to-CPU
> > interrupts.
>
> [Frank Li] I think the only limitation is only 4 irq numbers.
> The principle CPU to CPU irq is the same as MSI.

Not quite. Normal MSIs are device-to-CPU. CPU-to-CPU are normally
IPIs, and this one falls in the middle.

> What's your preferred help description?

<quote>
Provide a driver for the MU block used as a CPU-to-CPU MSI
controller. This requires a specially crafted DT to make use
of this driver.

If unsure, say N.
</quote>

M.

--
Without deviation from the norm, progress is not possible.