Re: [PATCH 2/3] irqchip/gic-v3: Add Renesas R-Car Gen4 erratum workaround

[Marek Vasut]

On 6/18/26 10:38 AM, Marc Zyngier wrote:

Hello Marc,

> > > > Renesas R-Car S4/V4H/V4M GIC600 integration has address width for AXI
> > > > or APB interface configured to 32 bit, it can therefore access only
> > > > the first 4 GiB of physical address space. This information comes from
> > > > R-Car V4H Interface Specification sheet, there is currently no technical
> > > > update number assigned to this limitation. Further input from hardware
> > > > engineer indicates that this limitation also applies to R-Car S4 and V4M.
> > > > Name the limitation GEN4GICITS1, and add a driver quirk to mitigate this
> > > > limitation.
> >
> > My concern is this ^ , I do not have an erratum number, because there
> > isn't one. I am in touch with the hardware engineer and I did get a
> > glimpse at internal details of the three SoC, which confirm the
> > limitations. Is this sufficient ?
>
> To be honest, this is between you and the SoC vendor. I'll take
> whatever symbol you come up with at face value, and will assume that
> the vendor agrees with it. After all, they are on Cc and have their
> SoB on the patch.

All right.

> > > > Note that the 0x0201743b GIC600 ID is not Renesas-specific, it is
> > > > common for many ARM GICv3 implementations. Therefore, add an extra
> > >
> > > Not quite. It designates GIC600 unambiguously.
> >
> > What I am trying to communicate is, that the 0x0201743b ID is not ID
> > of the Renesas GIC implementation, but it is a generic ARM GIC600
> > ID. That is why we cannot match the quirk on the ID (it is generic ARM
> > GIC600 ID), and instead we have to match the quirk on the [ ID
> > combined with of_machine_is_compatible("renesas,...") ].
>
> This is understood, and is no different from the other broken
> platforms in the tree.
>
> > > It is just that GIC600
> > > is integrated in zillions of SoCs, most of which don't have this
> > > problem (the machine I'm typing this from has a GIC600 *and* 96GB of
> > > RAM).
> >
> > Right.
> >
> > Shall I reword this paragraph somehow to make it clearer ?
>
> I'd simply say that the workaround is keyed on the combination of the
> GIC implementation and the platform identification in the device tree.

OK

> > > > of_machine_is_compatible() check.
> > > >
> > > > The GIC600 implementation in R-Car S4/V4H/V4M is r1p6.
> > >
> > > Is this relevant?
> >
> > I included it for the sake of completeness and to provide all relevant
> > information, based on previous discussions about similar limitations
> > that I could find on lore.k.o
>
> This information is already contained in the ID you quote (bits
> [19:12]), and can be decoded using the public TRM [1].
I'll drop it then.

Thanks