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.

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

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

> Hi, sunilvl

> Based on the above patch, I understand that you previously >resolved dependencies between Link devices and PCI Host Bridges by >calling acpi_dev_clear_dependencies(device). I would like to ask: >on RISC‑V platforms, if we need to manage dependencies between >multiple PCI Host Bridges, could this be addressed by adding a >call to acpi_dev_clear_dependencies(device) at the end of the >acpi_pci_root_add enumeration function?

> Initialization order dependencies can be defined via the ACPI >_DEP method in the DSDT. For example, if host bridge B depends on >host bridge A, bridge B should not be enumerated until bridge A is >fully initialized.

> Yes, that should work.
> Regards,
> Sunil

Hi,Sunil

I'm truly honored by your affirmation of my answer.Do you think this solution has a chance of being accepted into the upstream kernel? Are there any unintended side effects we may have overlooked?

Regards,
Yuye

On Mon, Dec 01, 2025 at 10:12:29PM +0800, huyuye wrote:
> > Hi, sunilvl
> 
> > Based on the above patch, I understand that you previously >resolved dependencies between Link devices and PCI Host Bridges by >calling acpi_dev_clear_dependencies(device). I would like to ask: >on RISC‑V platforms, if we need to manage dependencies between >multiple PCI Host Bridges, could this be addressed by adding a >call to acpi_dev_clear_dependencies(device) at the end of the >acpi_pci_root_add enumeration function?
> 
> > Initialization order dependencies can be defined via the ACPI >_DEP method in the DSDT. For example, if host bridge B depends on >host bridge A, bridge B should not be enumerated until bridge A is >fully initialized.
> 
> > Yes, that should work.
> > Regards,
> > Sunil
> 
> Hi,Sunil
> 
> I'm truly honored by your affirmation of my answer.Do you think this solution has a chance of being accepted into the upstream kernel? Are there any unintended side effects we may have overlooked?
> 
Acceptance of this solution depends on the PCI/ACPI maintainers. To help
them evaluate it, you should clearly describe why your platform requires
this dependency in the patch.

Regards
Sunil

Hi, sunilvl

Based on the above patch, I understand that you previously resolved dependencies between Link devices and PCI Host Bridges by calling acpi_dev_clear_dependencies(device). I would like to ask: on RISC‑V platforms, if we need to manage dependencies between multiple PCI Host Bridges, could this be addressed by adding a call to acpi_dev_clear_dependencies(device) at the end of the acpi_pci_root_add enumeration function?

Initialization order dependencies can be defined via the ACPI _DEP method in the DSDT. For example, if host bridge B depends on host bridge A, bridge B should not be enumerated until bridge A is fully initialized.

Best regards,
Yuye

On Mon, Dec 01, 2025 at 09:07:55PM +0800, huyuye wrote:
> Hi, sunilvl
> 
> Based on the above patch, I understand that you previously resolved dependencies between Link devices and PCI Host Bridges by calling acpi_dev_clear_dependencies(device). I would like to ask: on RISC‑V platforms, if we need to manage dependencies between multiple PCI Host Bridges, could this be addressed by adding a call to acpi_dev_clear_dependencies(device) at the end of the acpi_pci_root_add enumeration function?
> 
> Initialization order dependencies can be defined via the ACPI _DEP method in the DSDT. For example, if host bridge B depends on host bridge A, bridge B should not be enumerated until bridge A is fully initialized.
> 
Yes, that should work.

Regards,
Sunil

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
>