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

From: Bjorn Helgaas <helgaas@kernel.org>
To: Sunil V L <sunilvl@ventanamicro.com>
Cc: linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org,
	linux-acpi@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-serial@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Len Brown <lenb@kernel.org>, Bjorn Helgaas <bhelgaas@google.com>,
	Anup Patel <anup@brainfault.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Jiri Slaby <jirislaby@kernel.org>,
	Conor Dooley <conor.dooley@microchip.com>,
	Andrew Jones <ajones@ventanamicro.com>,
	Atish Kumar Patra <atishp@rivosinc.com>,
	Haibo Xu <haibo1.xu@intel.com>
Subject: Re: [RFC PATCH v2 06/21] RISC-V: Kconfig: Select deferred GSI probe for ACPI systems
Date: Thu, 26 Oct 2023 12:04:08 -0500	[thread overview]
Message-ID: <20231026170408.GA1825378@bhelgaas> (raw)
In-Reply-To: <20231025202344.581132-7-sunilvl@ventanamicro.com>

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@ventanamicro.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
> 
> 
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