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

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Date:   Thu, 26 Oct 2023 12:04:08 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sunil V L <sunilvl@...tanamicro.com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-serial@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Len Brown <lenb@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Anup Patel <anup@...infault.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Conor Dooley <conor.dooley@...rochip.com>,
        Andrew Jones <ajones@...tanamicro.com>,
        Atish Kumar Patra <atishp@...osinc.com>,
        Haibo Xu <haibo1.xu@...el.com>
Subject: Re: [RFC PATCH v2 06/21] RISC-V: Kconfig: Select deferred GSI probe
 for ACPI systems

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@...tanamicro.com>
> ---
>  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
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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