linux-kernel - Re: [PATCH v5 08/17] ACPI: pci_link: Clear the dependencies after probe

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Date: Thu, 2 May 2024 15:02:33 +0530
From: Sunil V L <sunilvl@...tanamicro.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Bjorn Helgaas <helgaas@...nel.org>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-riscv@...ts.infradead.org, linux-acpi@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-serial@...r.kernel.org,
	acpica-devel@...ts.linux.dev,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Paul Walmsley <paul.walmsley@...ive.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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jirislaby@...nel.org>,
	Robert Moore <robert.moore@...el.com>,
	Conor Dooley <conor.dooley@...rochip.com>,
	Andrew Jones <ajones@...tanamicro.com>,
	Marc Zyngier <maz@...nel.org>,
	Atish Kumar Patra <atishp@...osinc.com>,
	Andrei Warkentin <andrei.warkentin@...el.com>,
	Haibo1 Xu <haibo1.xu@...el.com>,
	Björn Töpel <bjorn@...nel.org>
Subject: Re: [PATCH v5 08/17] ACPI: pci_link: Clear the dependencies after
 probe

On Thu, May 02, 2024 at 12:25:35PM +0300, Andy Shevchenko wrote:
> On Wed, May 01, 2024 at 11:56:15AM -0500, Bjorn Helgaas wrote:
> > On Wed, May 01, 2024 at 05:47:33PM +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.
> > > 
> > > So, add the link device's HID to dependency honor list and also clear it
> > > after its probe.
> > > 
> > > Since this is required only for architectures like RISC-V, enable this
> > > code under a new config option and set this only in RISC-V.
> 
> ...
> 
> > > +	if (IS_ENABLED(CONFIG_ARCH_ACPI_DEFERRED_GSI))
> > > +		acpi_dev_clear_dependencies(device);
> > 
> > This is really a question for Rafael, but it doesn't seem right that
> > this completely depends on a config option.
> 
> +1 here, fells like a hack and looks like a hack.
> 
I can remove the config option. I just thought this would probably never
required to be called on other architectures.

Unless there is an objection, I will remove it in next version.

Thanks!
Sunil
> > Is there a reason this wouldn't work for all architectures, i.e., what
> > would happen if you just called acpi_dev_clear_dependencies()
> > unconditionally?
> 
> -- 
> With Best Regards,
> Andy Shevchenko
> 
>