[PATCH v2 2/5] irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/ firmware issues

[Geert Uytterhoeven]

Hi Marc,

On Tue, May 30, 2023 at 11:46 AM Marc Zyngier <maz at kernel.org> wrote:
> On Tue, 30 May 2023 09:29:02 +0100,
> Geert Uytterhoeven <geert at linux-m68k.org> wrote:
> > On Mon, May 15, 2023 at 10:16 PM Douglas Anderson <dianders at chromium.org> wrote:
> > > Some Chromebooks with Mediatek SoCs have a problem where the firmware
> > > doesn't properly save/restore certain GICR registers. Newer
> > > Chromebooks should fix this issue and we may be able to do firmware
> > > updates for old Chromebooks. At the moment, the only known issue with
> > > these Chromebooks is that we can't enable "pseudo NMIs" since the
> > > priority register can be lost. Enabling "pseudo NMIs" on Chromebooks
> > > with the problematic firmware causes crashes and freezes.
> > >
> > > Let's detect devices with this problem and then disable "pseudo NMIs"
> > > on them. We'll detect the problem by looking for the presence of the
> > > "mediatek,broken-save-restore-fw" property in the GIC device tree
> > > node. Any devices with fixed firmware will not have this property.
> > >
> > > Our detection plan works because we never bake a Chromebook's device
> > > tree into firmware. Instead, device trees are always bundled with the
> > > kernel. We'll update the device trees of all affected Chromebooks and
> > > then we'll never enable "pseudo NMI" on a kernel that is bundled with
> > > old device trees. When a firmware update is shipped that fixes this
> > > issue it will know to patch the device tree to remove the property.
> > >
> > > In order to make this work, the quick detection mechanism of the GICv3
> > > code is extended to be able to look for properties in addition to
> > > looking at "compatible".
> > >
> > > Reviewed-by: Julius Werner <jwerner at chromium.org>
> > > Signed-off-by: Douglas Anderson <dianders at chromium.org>
> > > ---
> > >
> > > Changes in v2:
> > > - mediatek,gicr-save-quirk => mediatek,broken-save-restore-fw
> >
> > Thanks for your patch, which is now commit 44bd78dd2b8897f5
> > ("irqchip/gic-v3: Disable pseudo NMIs on Mediatek devices w/
> > firmware issues") in v6.4-rc4.
> >
> > This causes enabling an unrelated workaround on R-Car V4H:
> >
> >     GIC: enabling workaround for GICv3: Cavium erratum 38539
> >
> > > --- a/drivers/irqchip/irq-gic-common.c
> > > +++ b/drivers/irqchip/irq-gic-common.c
> > > @@ -16,7 +16,11 @@ void gic_enable_of_quirks(const struct device_node *np,
> > >                           const struct gic_quirk *quirks, void *data)
> > >  {
> > >         for (; quirks->desc; quirks++) {
> > > -               if (!of_device_is_compatible(np, quirks->compatible))
> > > +               if (quirks->compatible &&
> > > +                   !of_device_is_compatible(np, quirks->compatible))
> > > +                       continue;
> > > +               if (quirks->property &&
> > > +                   !of_property_read_bool(np, quirks->property))
> > >                         continue;
> >
> > Presumably the loop should continue if none of quirks-compatible
> > or quirks->property is set?
>
> Indeed, thanks for pointing that out. Can you give the following hack
> a go (compile tested only)?
>
> diff --git a/drivers/irqchip/irq-gic-common.c b/drivers/irqchip/irq-gic-common.c
> index de47b51cdadb..7b591736ab58 100644
> --- a/drivers/irqchip/irq-gic-common.c
> +++ b/drivers/irqchip/irq-gic-common.c
> @@ -16,6 +16,8 @@ void gic_enable_of_quirks(const struct device_node *np,
>                           const struct gic_quirk *quirks, void *data)
>  {
>         for (; quirks->desc; quirks++) {
> +               if (!quirks->compatible && !quirks->property)
> +                       continue;
>                 if (quirks->compatible &&
>                     !of_device_is_compatible(np, quirks->compatible))
>                         continue;
>
> If that works for you, I'll queue it ASAP.

Thanks, that fixes the issue for me on Renesas White-Hawk (R-Car V4H).
No regressions on Koelsch (R-Car M2-W) and Salvator-XS (R-Car H3 ES2.0).
Tested-by: Geert Uytterhoeven <geert+renesas at glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds