Re: [PATCH v7 08/17] ACPI: pci_link: Clear the dependencies after probe

From: Bjorn Helgaas <helgaas@kernel.org>
To: Sunil V L <sunilvl@ventanamicro.com>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-riscv@lists.infradead.org, linux-pci@vger.kernel.org,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	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>,
	Samuel Holland <samuel.holland@sifive.com>,
	Robert Moore <robert.moore@intel.com>,
	Conor Dooley <conor.dooley@microchip.com>,
	Andrew Jones <ajones@ventanamicro.com>,
	Haibo Xu <haibo1.xu@intel.com>,
	Atish Kumar Patra <atishp@rivosinc.com>,
	Drew Fustini <dfustini@tenstorrent.com>
Subject: Re: [PATCH v7 08/17] ACPI: pci_link: Clear the dependencies after probe
Date: Wed, 31 Jul 2024 14:49:27 -0500	[thread overview]
Message-ID: <20240731194927.GA78106@bhelgaas> (raw)
In-Reply-To: <20240729142241.733357-9-sunilvl@ventanamicro.com>

On Mon, Jul 29, 2024 at 07:52:30PM +0530, Sunil V L wrote:
> RISC-V platforms need to use dependencies between PCI host bridge, Link
> devices and the interrupt controllers to ensure probe order. The
> dependency is like below.
> 
> Interrupt controller <-- Link Device <-- PCI Host bridge.
> 
> If there is no dependency added between Link device and PCI Host Bridge,
> then the PCI end points can get probed prior to link device, unable to
> get mapping for INTx.

This sentence is missing a word or something.  Maybe it's supposed to
say something like this:

  If there is no dependency between Link device and PCI Host Bridge,
  then PCI devices may be probed prior to Link devices.  If a PCI
  device is probed before its Link device, we won't be able to find
  its INTx mapping.

> So, add the link device's HID to dependency honor list and also clear it
> after its probe.

It looks like *this* patch only clears it after probe.  And the commit
log doesn't say why we need to clear the dependency.

> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> ---
>  drivers/acpi/pci_link.c | 2 ++
>  drivers/acpi/scan.c     | 1 +
>  2 files changed, 3 insertions(+)
> 
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index aa1038b8aec4..b727db968f33 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -748,6 +748,8 @@ static int acpi_pci_link_add(struct acpi_device *device,
>  	if (result)
>  		kfree(link);
>  
> +	acpi_dev_clear_dependencies(device);
> +
>  	return result < 0 ? result : 1;
>  }
>  
> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
> index 28a221f956d7..753539a1f26b 100644
> --- a/drivers/acpi/scan.c
> +++ b/drivers/acpi/scan.c
> @@ -863,6 +863,7 @@ static const char * const acpi_honor_dep_ids[] = {
>  	"INTC10CF", /* IVSC (MTL) driver must be loaded to allow i2c access to camera sensors */
>  	"RSCV0001", /* RISC-V PLIC */
>  	"RSCV0002", /* RISC-V APLIC */
> +	"PNP0C0F",  /* PCI Link Device */
>  	NULL
>  };
>  
> -- 
> 2.43.0
> 