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

[Bjorn Helgaas]

On Fri, Aug 23, 2024 at 12:03:25PM +0530, Sunil V L wrote:
> On Thu, Aug 22, 2024 at 04:44:15PM -0500, Bjorn Helgaas wrote:
> > 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"?
> >
> Okay. Let me move this to the patch you suggested.

Given my forgetfulness and your pointing out that this *does* add the
dependencies (by virtue of adding PNP0C0F to the acpi_honor_dep_ids[]
list), it does make sense here.

> > > 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.

Maybe expanding this to "Add the link devices HID (PNP0C0F) to the
acpi_honor_dep_ids[] dependency list" would help connect this all
together?

> > This still claims this patch adds HID, which I don't think it does.
> >
> Please see below.
>  
> > > Signed-off-by: Sunil V L <sunilvl@xxxxxxxxxxxxxxxx>
> > > Tested-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
> > > ---
> > >  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 */
>
> This is the change which I meant adding HID to the honor list. Do you
> recommend to make this change separate patch so that it doesn't confuse
> with adding a new HID to the probe match table?

Oh, right, sorry.  I remember working this out in the past, but I had
forgotten.

I think it makes sense in this patch because the add and removal are
matched when they're in the same patch.

Sorry for the noise!

Bjorn