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

[<Conor.Dooley@microchip.com>]

On 20/08/2022 07:54, Anup Patel wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> 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();
>  }
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