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

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Message-ID: <ZsgtNbBLfP3SygYv@sunil-laptop>
Date: Fri, 23 Aug 2024 12:03:25 +0530
From: Sunil V L <sunilvl@...tanamicro.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
	acpica-devel@...ts.linux.dev, Will Deacon <will@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Anup Patel <anup@...infault.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Samuel Holland <samuel.holland@...ive.com>,
	Robert Moore <robert.moore@...el.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Haibo Xu <haibo1.xu@...el.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Atish Kumar Patra <atishp@...osinc.com>,
	Drew Fustini <dfustini@...storrent.com>,
	Björn Töpel <bjorn@...osinc.com>
Subject: Re: [PATCH v8 08/17] ACPI: pci_link: Clear the dependencies after
 probe

Hi Bjorn,

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.
 
> > 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.
>
Please see below.
 
> > Signed-off-by: Sunil V L <sunilvl@...tanamicro.com>
> > Tested-by: BjÃ¶rn TÃ¶pel <bjorn@...osinc.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 */
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?

Thanks!
Sunil