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

[Guo Ren]

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.

>
> 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/