Re: [PATCH v8 4/7] RISC-V: Treat IPIs as normal Linux IRQs

Conor.Dooley
2022-08-26T19:11:06Z

On 20/08/2022 07:54, Anup Patel wrote:
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>
> Currently, the RISC-V kernel provides arch specific hooks (i.e.
> struct riscv_ipi_ops) to register IPI handling methods. The stats
> gathering of IPIs is also arch specific in the RISC-V kernel.
>
> Other architectures (such as ARM, ARM64, and MIPS) have moved away
> from custom arch specific IPI handling methods. Currently, these
> architectures have Linux irqchip drivers providing a range of Linux
> IRQ numbers to be used as IPIs and IPI triggering is done using
> generic IPI APIs. This approach allows architectures to treat IPIs
> as normal Linux IRQs and IPI stats gathering is done by the generic
> Linux IRQ subsystem.
>
> We extend the RISC-V IPI handling as-per above approach so that arch
> specific IPI handling methods (struct riscv_ipi_ops) can be removed
> and the IPI handling is done through the Linux IRQ subsystem.
>
> Signed-off-by: Anup Patel <apatel@ventanamicro.com>

> +void riscv_ipi_set_virq_range(int virq, int nr)
> +{
> + int i, err;
>
> - if (ops & (1 << IPI_IRQ_WORK)) {
> - stats[IPI_IRQ_WORK]++;
> - irq_work_run();
> - }
> + if (WARN_ON(ipi_virq_base))
> + return;
>
> -#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
> - if (ops & (1 << IPI_TIMER)) {
> - stats[IPI_TIMER]++;
> - tick_receive_broadcast();
> - }
> -#endif
> - BUG_ON((ops >> IPI_MAX) != 0);
> + WARN_ON(nr < IPI_MAX);
> + nr_ipi = min(nr, IPI_MAX);
> + ipi_virq_base = virq;
> +
> + /* Request IPIs */
> + for (i = 0; i < nr_ipi; i++) {
> + err = request_percpu_irq(ipi_virq_base + i, handle_IPI,
> + "IPI", &ipi_virq_base);

FWIW, ?sparse? does not like this:
arch/riscv/kernel/smp.c:163:50: warning: incorrect type in argument 4 (different address spaces)
arch/riscv/kernel/smp.c:163:50: expected void [noderef] __percpu *percpu_dev_id
arch/riscv/kernel/smp.c:163:50: got int *

> + WARN_ON(err);
>
> - /* Order data access and bit testing. */
> - mb();
> + ipi_desc[i] = irq_to_desc(ipi_virq_base + i);
> + irq_set_status_flags(ipi_virq_base + i, IRQ_HIDDEN);
> }
> +
> + /* Enabled IPIs for boot CPU immediately */
> + riscv_ipi_enable();
> }