[PATCH] utils: irqchip: plic: Using 1 as default priority value

[Atish Patra]

On Sat, Apr 24, 2021 at 12:07 AM Guo Ren <guoren at kernel.org> wrote:
>
> Hi Anup,
>
> On Sat, Apr 24, 2021 at 12:04 PM Anup Patel <Anup.Patel at wdc.com> wrote:
> >
> >
> >
> > > -----Original Message-----
> > > From: guoren at kernel.org <guoren at kernel.org>
> > > Sent: 24 April 2021 08:14
> > > To: guoren at kernel.org; anup at brainfault.org
> > > Cc: opensbi at lists.infradead.org; Guo Ren <guoren at linux.alibaba.com>;
> > > Anup Patel <Anup.Patel at wdc.com>
> > > Subject: [PATCH] utils: irqchip: plic: Using 1 as default priority value
> > >
> > > From: Guo Ren <guoren at linux.alibaba.com>
> > >
> > > In linux plic drivers:
> > > static inline void plic_irq_toggle(const struct cpumask *mask,
> > >                                  struct irq_data *d, int enable)
> > > {
> > >       int cpu;
> > >       struct plic_priv *priv = irq_data_get_irq_chip_data(d);
> > >
> > >       writel(enable, priv->regs + PRIORITY_BASE + d->hwirq *
> > > PRIORITY_PER_ID);
> > >
> > > It sets PRIORITY in enable/disable irq, but not during init.
> > > Actually, priority is no use at all and just keep them the same is enough.
> > >
> > > The motivation of my patch: When we want to run 2 different Linux OS in the
> > > same SMP system, the second Linux cold boot will flush all priority to zero
> > > and the patch is to solve the problem.
> >
> > Don't create separate OpenSBI instances for 2 different OSes.
> >
> > The OpenSBI domain support allows you to create 2 different domains
> > for each Linux. Please checkout recent YouTube video on OpenSBI domains
> I agree with the idea of OpenSBI domains, but it isn't related to the patch.
>
> What we've done in a 4 cores SMP with 8GB memory system is:
>
>  - "hart0 + hart1, with memory 0 - 4GB" run linux1 + opensbi1
>  - "hart2 + hart3" with memory 4GB - 8GB run linux2 + opensbi2
>
> They are physical separated in memory and CPUs, but plic is shared.
> Current opensbi + Linux almost could natively support this kind of
> simple scenario, but this patch.
>

I am just curious about the use case. Why do you need to run two
different linux instances ?

> >
> > Regards,
> > Anup
> >
> > >
> > > Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> > > Cc: Anup Patel <anup.patel at wdc.com>
> > > ---
> > >  lib/utils/irqchip/plic.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/lib/utils/irqchip/plic.c b/lib/utils/irqchip/plic.c index
> > > 7665c62..70e89a6 100644
> > > --- a/lib/utils/irqchip/plic.c
> > > +++ b/lib/utils/irqchip/plic.c
> > > @@ -94,7 +94,7 @@ int plic_cold_irqchip_init(struct plic_data *plic)
> > >
> > >       /* Configure default priorities of all IRQs */
> > >       for (i = 1; i <= plic->num_src; i++)
> > > -             plic_set_priority(plic, i, 0);
> > > +             plic_set_priority(plic, i, 1);
> > >
> > >       return 0;
> > >  }
> > > --
> > > 2.7.4
> >
>
>
> --
> Best Regards
>  Guo Ren
>
> ML: https://lore.kernel.org/linux-csky/
>
> --
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-- 
Regards,
Atish