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SubjectRe: [PATCH 2/6] irqchip/riscv-intc: Set intc domain as the default host
On Tue, Jan 25, 2022 at 11:47 PM Marc Zyngier <maz@kernel.org> wrote:
>
> On Tue, 25 Jan 2022 05:42:13 +0000,
> Anup Patel <apatel@ventanamicro.com> wrote:
> >
> > We have quite a few RISC-V drivers (such as RISC-V SBI IPI driver,
> > RISC-V timer driver, RISC-V PMU driver, etc) which do not have a
> > dedicated DT/ACPI fwnode. This patch makes intc domain as the default
> > host so that these drivers can directly create local interrupt mapping
> > using standardized local interrupt numbers
> >
> > Signed-off-by: Anup Patel <apatel@ventanamicro.com>
> > ---
> > drivers/clocksource/timer-riscv.c | 17 +----------------
> > drivers/irqchip/irq-riscv-intc.c | 9 +++++++++
> > 2 files changed, 10 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/clocksource/timer-riscv.c b/drivers/clocksource/timer-riscv.c
> > index 1767f8bf2013..dd6916ae6365 100644
> > --- a/drivers/clocksource/timer-riscv.c
> > +++ b/drivers/clocksource/timer-riscv.c
> > @@ -102,8 +102,6 @@ static irqreturn_t riscv_timer_interrupt(int irq, void *dev_id)
> > static int __init riscv_timer_init_dt(struct device_node *n)
> > {
> > int cpuid, hartid, error;
> > - struct device_node *child;
> > - struct irq_domain *domain;
> >
> > hartid = riscv_of_processor_hartid(n);
> > if (hartid < 0) {
> > @@ -121,20 +119,7 @@ static int __init riscv_timer_init_dt(struct device_node *n)
> > if (cpuid != smp_processor_id())
> > return 0;
> >
> > - domain = NULL;
> > - child = of_get_compatible_child(n, "riscv,cpu-intc");
> > - if (!child) {
> > - pr_err("Failed to find INTC node [%pOF]\n", n);
> > - return -ENODEV;
> > - }
> > - domain = irq_find_host(child);
> > - of_node_put(child);
> > - if (!domain) {
> > - pr_err("Failed to find IRQ domain for node [%pOF]\n", n);
> > - return -ENODEV;
> > - }
> > -
> > - riscv_clock_event_irq = irq_create_mapping(domain, RV_IRQ_TIMER);
> > + riscv_clock_event_irq = irq_create_mapping(NULL, RV_IRQ_TIMER);
> > if (!riscv_clock_event_irq) {
> > pr_err("Failed to map timer interrupt for node [%pOF]\n", n);
> > return -ENODEV;
> > diff --git a/drivers/irqchip/irq-riscv-intc.c b/drivers/irqchip/irq-riscv-intc.c
> > index b65bd8878d4f..9f0a7a8a5c4d 100644
> > --- a/drivers/irqchip/irq-riscv-intc.c
> > +++ b/drivers/irqchip/irq-riscv-intc.c
> > @@ -125,6 +125,15 @@ static int __init riscv_intc_init(struct device_node *node,
> > return rc;
> > }
> >
> > + /*
> > + * Make INTC as the default domain which will allow drivers
> > + * not having dedicated DT/ACPI fwnode (such as RISC-V SBI IPI
> > + * driver, RISC-V timer driver, RISC-V PMU driver, etc) can
> > + * directly create local interrupt mapping using standardized
> > + * local interrupt numbers.
> > + */
> > + irq_set_default_host(intc_domain);
>
> No, please. This really is a bad idea. This sort of catch-all have
> constantly proven to be a nuisance, because they discard all the
> topology information. Eventually, you realise that you need to know
> where this is coming from, but it really is too late.
>
> I'd rather you *synthesise* a fwnode (like ACPI does) rather then do
> this.

In absence of INTC as the default domain, currently we have various
drivers looking up INTC irq_domain from DT (or ACPI). This is quite a
bit of duplicate code across various drivers.

How about having a irq_domain lookup routine (riscv_intc_find_irq_domain())
exported by the RISC-V INTC driver or arch/riscv ?
OR
Do you have an alternative suggestion ?

Regards,
Anup

>
> M.
>
> --
> Without deviation from the norm, progress is not possible.

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