Re: [PATCH] irqchip/gic-v3-its: Mark GIC as non-shareable by OF property

[Lorenzo Pieralisi]

On Mon, Sep 04, 2023 at 08:24:51AM +0100, Marc Zyngier wrote:
> On Mon, 04 Sep 2023 03:04:31 +0100,
> Fang Xiang <fangxiang3@xxxxxxxxxx> wrote:
> > 
> > GIC600/GIC700 integration in some platforms does not support the
> > sharability feature. Commit a8707f553884 ("irqchip/gic-v3: Add
> > Rockchip 3588001 erratum workaround") added flags to indicate the
> > integration design error, but the quirk is just applied with
> > RK3588/RK3588S and GIC600.
> > 
> > The property are named "force-non-shareable" to be vendor agnostic,
> > since apparently similar integration design errors exist in other
> > platforms and they can reuse the same property in their GIC ITS
> > device-node.
> 
> No. If this is a problem, this must be dealt with in the following
> manner:
> 
> - a standard property, which is documented in the ITS binding
> - an equivalent ACPI property, equally documented
> - separate instances of the property for the core GIC and the ITS
>   (because the RDs are *not* defined at the ITS level)

I am about to post a patchset to start discussion on how to "fix"
these designs (in DT - ACPI will follow the approach we agree on),
let's take it from there.

Thanks,
Lorenzo

> > Signed-off-by: Fang Xiang <fangxiang3@xxxxxxxxxx>
> > ---
> >  drivers/irqchip/irq-gic-v3-its.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> > index e0c2b10d154d..2e92eac1e5f3 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -5055,6 +5055,16 @@ static int __init its_compute_its_list_map(struct resource *res,
> >         return its_number;
> >  }
> > 
> > +static void its_of_update_shareability(struct its_node *its)
> > +{
> > +       if (!fwnode_property_present(its->fwnode_handle,
> > +                               "force-non-shareable"))
> > +               return;
> > +
> > +       its->flags |= ITS_FLAGS_FORCE_NON_SHAREABLE;
> > +       gic_rdists->flags |= RDIST_FLAGS_FORCE_NON_SHAREABLE;
> 
> There is no reason why we should conflate the two, other than your
> implementation being monolithic.
> 
> > +}
> > +
> >  static int __init its_probe_one(struct resource *res,
> >                                 struct fwnode_handle *handle, int numa_node)
> >  {
> > @@ -5130,6 +5140,7 @@ static int __init its_probe_one(struct resource *res,
> >         its->msi_domain_flags = IRQ_DOMAIN_FLAG_ISOLATED_MSI;
> > 
> >         its_enable_quirks(its);
> > +       its_of_update_shareability(its);
> 
> As mentioned above, we need a mechanism that works across firmware implementations.
> 
> > 
> >         err = its_alloc_tables(its);
> >         if (err)
> > --
> > 2.34.1
> > 
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> \
> 
> Please fix your email setup.
> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.