Re: [PATCH v8 08/17] ACPI: pci_link: Clear the dependencies after probe

[Bjorn Helgaas <helgaas@kernel.org>]

On Mon, Aug 12, 2024 at 06:29:20AM +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 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.

This seems to explain why we want these dependencies, which is useful,
but *this* patch only removes the dependencies.

Maybe this description should be in the patch that *adds* the
dependencies, e.g., "ACPI: RISC-V: Implement function to add implicit
dependencies"?

> So, add the link device's HID to dependency honor list and clear the
> dependency after probe is done so that the dependent devices are
> unblocked to probe.

This still claims this patch adds HID, which I don't think it does.

> Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
> Tested-by: Björn Töpel <bjorn@rivosinc.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
>