[PATCH V6 2/2] irqchip/sifive-plic: Fixup thead,c900-plic dt parse in opensbi

[Guo Ren]

On Sun, Jan 30, 2022 at 10:50 AM Samuel Holland <samuel at sholland.org> wrote:
>
> On 1/29/22 8:08 PM, Guo Ren wrote:
> > On Sun, Jan 30, 2022 at 2:32 AM Marc Zyngier <maz at kernel.org> wrote:
> >>
> >> On Sat, 29 Jan 2022 16:27:26 +0000,
> >> guoren at kernel.org wrote:
> >>>
> >>> From: Guo Ren <guoren at linux.alibaba.com>
> >>>
> >>> The thead,c900-plic has been used in opensbi to distinguish
> >>> PLIC [1]. Although PLICs have the same behaviors in Linux,
> >>> they are different hardware with some custom initializing in
> >>> firmware(opensbi).
> >>>
> >>> [1]: https://github.com/riscv-software-src/opensbi/commit/78c2b19218bd62653b9fb31623a42ced45f38ea6
> >>>
> >>> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> >>> Cc: Anup Patel <anup at brainfault.org>
> >>> Cc: Marc Zyngier <maz at kernel.org>
> >>> Cc: Palmer Dabbelt <palmer at dabbelt.com>
> >>> Cc: Samuel Holland <samuel at sholland.org>
> >>> Cc: Thomas Gleixner <tglx at linutronix.de>
> >>> ---
> >>>  drivers/irqchip/irq-sifive-plic.c | 25 +++++++++++++++++++++++--
> >>>  1 file changed, 23 insertions(+), 2 deletions(-)
> >>>
> >>> diff --git a/drivers/irqchip/irq-sifive-plic.c b/drivers/irqchip/irq-sifive-plic.c
> >>> index 259065d271ef..245655928076 100644
> >>> --- a/drivers/irqchip/irq-sifive-plic.c
> >>> +++ b/drivers/irqchip/irq-sifive-plic.c
> >>> @@ -172,7 +172,7 @@ static void plic_irq_eoi(struct irq_data *d)
> >>>       }
> >>>  }
> >>>
> >>> -static struct irq_chip plic_chip = {
> >>> +static struct irq_chip sifive_plic_chip = {
> >>>       .name           = "SiFive PLIC",
> >>>       .irq_mask       = plic_irq_mask,
> >>>       .irq_unmask     = plic_irq_unmask,
> >>> @@ -182,12 +182,24 @@ static struct irq_chip plic_chip = {
> >>>  #endif
> >>>  };
> >>>
> >>> +static struct irq_chip thead_plic_chip = {
> >>> +     .name           = "T-Head PLIC",
> >>> +     .irq_mask       = plic_irq_mask,
> >>> +     .irq_unmask     = plic_irq_unmask,
> >>> +     .irq_eoi        = plic_irq_eoi,
> >>> +#ifdef CONFIG_SMP
> >>> +     .irq_set_affinity = plic_set_affinity,
> >>> +#endif
> >>> +};
> >>
> >> For pure entertainment, let's compare the two structures:
> >>
> >> static struct irq_chip plic_chip = {
> >>         .name           = "SiFive PLIC",
> >>         .irq_mask       = plic_irq_mask,
> >>         .irq_unmask     = plic_irq_unmask,
> >>         .irq_eoi        = plic_irq_eoi,
> >> #ifdef CONFIG_SMP
> >>         .irq_set_affinity = plic_set_affinity,
> >> #endif
> >> };
> >>
> >> Oh wait: a string. Must be really important. Not.
> > No, pls see below comment.
> >
> >>
> >>> +
> >>> +static struct irq_chip *def_plic_chip = &sifive_plic_chip;
> >>> +
> >>>  static int plic_irqdomain_map(struct irq_domain *d, unsigned int irq,
> >>>                             irq_hw_number_t hwirq)
> >>>  {
> >>>       struct plic_priv *priv = d->host_data;
> >>>
> >>> -     irq_domain_set_info(d, irq, hwirq, &plic_chip, d->host_data,
> >>> +     irq_domain_set_info(d, irq, hwirq, def_plic_chip, d->host_data,
> >>>                           handle_fasteoi_irq, NULL, NULL);
> >>>       irq_set_noprobe(irq);
> >>>       irq_set_affinity(irq, &priv->lmask);
> >>> @@ -396,5 +408,14 @@ static int __init plic_init(struct device_node *node,
> >>>       return error;
> >>>  }
> >>>
> >>> +static int __init thead_c900_plic_init(struct device_node *node,
> >>> +             struct device_node *parent)
> >>> +{
> >>> +     def_plic_chip = &thead_plic_chip;
> >>> +
> >>> +     return plic_init(node, parent);
> >>> +}
> >>> +
> >>>  IRQCHIP_DECLARE(sifive_plic, "sifive,plic-1.0.0", plic_init);
> >>>  IRQCHIP_DECLARE(riscv_plic0, "riscv,plic0", plic_init); /* for legacy systems */
> >>> +IRQCHIP_DECLARE(thead_c900_plic, "thead,c900-plic", thead_c900_plic_init);
> >>
> >> Sorry, but I can't see any point to this patch.
> > You didn't see the link I've put in the patch. In that opensbi patch:
> >
> >                 intc: interrupt-controller at 10000000 {
> >                         #interrupt-cells = <1>;
> > -                       compatible = "riscv,plic0";
> > +                       compatible = "allwinner,sun20i-d1-plic",
> > +                                    "thead,c900-plic";
> >
> > +#define THEAD_PLIC_CTRL_REG 0x1ffffc
> > +
> > +static void thead_plic_plat_init(struct plic_data *pd)
> > +{
> > +       writel_relaxed(BIT(0), (void *)pd->addr + THEAD_PLIC_CTRL_REG);
> > +}
> > +
> >  static const struct fdt_match irqchip_plic_match[] = {
> >         { .compatible = "riscv,plic0" },
> >         { .compatible = "sifive,plic-1.0.0" },
> > +       { .compatible = "thead,c900-plic",
> > +         .data = thead_plic_plat_init },
> >         { },
> >  };
> >
> > We've changed the compatible name for thead,c900-plic, and there is no
> > riscv,plic0 / sifive,plic-1.0.0 in dts. Without the patch, the newest
> > opensbi + newest Linux would be broken in the Allwinner D1 dev board.
>
> Yes, some patch is still necessary, because the hardware is indeed incompatible
> with riscv,plic0. However, this driver does not care about the difference. So
> all you need to do is hook up the existing code to the new compatible:
>
> +IRQCHIP_DECLARE(thead_c900_plic, "thead,c900-plic", plic_init);
I think we should give clear info in /proc/interrupts. I hope we could
keep thead_plic_init.

>
> Regards,
> Samuel



-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/