Re: [RFC PATCH v2 06/21] RISC-V: Kconfig: Select deferred GSI probe for ACPI systems

[Bjorn Helgaas]

On Thu, Oct 26, 2023 at 01:53:29AM +0530, Sunil V L wrote:
> On RISC-V platforms, apart from root interrupt controllers (which
> provide local interrupts and IPI), other interrupt controllers in the
> hierarchy are probed late. Enable this select this CONFIG option for
> RISC-V platforms so that device drivers which connect to deferred
> interrupt controllers can take appropriate action.

Quite a bit of this series seems related to the question of interrupt
controllers being probed "late".

I don't see anything specific about *how* late this might be, but from
the use of -EPROBE_DEFER in individual drivers (8250_pnp explicitly,
and acpi_register_gsi() and pnp_irq() and acpi_pci_irq_enable(), which
are called from driver .probe() paths) it seems like interrupt
controllers might be detected even after devices that use them.

That seems like a fairly invasive change to the driver probe flow.
If we really need to do that, I think it might merit a little more
background as justification since we haven't had to do it for any
other arch yet.

Bjorn

> Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> ---
>  arch/riscv/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 8c105a151e12..b62441aefa6a 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -12,6 +12,7 @@ config 32BIT
>  
>  config RISCV
>  	def_bool y
> +	select ARCH_ACPI_DEFERRED_GSI if ACPI
>  	select ACPI_GENERIC_GSI if ACPI
>  	select ACPI_MCFG if (ACPI && PCI)
>  	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
> -- 
> 2.39.2
> 
> 
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