Re: [PATCH 06/15] PCI/ACPI: Link host bridge to its ACPI fw node

From: Robert Richter <rrichter@amd.com>
To: Dan Williams <dan.j.williams@intel.com>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>,
	Alison Schofield <alison.schofield@intel.com>,
	Vishal Verma <vishal.l.verma@intel.com>,
	Ira Weiny <ira.weiny@intel.com>,
	Ben Widawsky <bwidawsk@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>, <linux-cxl@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Len Brown <lenb@kernel.org>,
	Linux PCI <linux-pci@vger.kernel.org>,
	ACPI Devel Maling List <linux-acpi@vger.kernel.org>
Subject: Re: [PATCH 06/15] PCI/ACPI: Link host bridge to its ACPI fw node
Date: Fri, 9 Sep 2022 12:20:45 +0200	[thread overview]
Message-ID: <YxsTfVdOgc9sOOVm@rric.localdomain> (raw)
In-Reply-To: <631a464c166cc_166f294d5@dwillia2-xfh.jf.intel.com.notmuch>

On 08.09.22 12:45:16, Dan Williams wrote:
> Rafael J. Wysocki wrote:
> > On Thu, Sep 8, 2022 at 8:05 AM Dan Williams <dan.j.williams@intel.com> wrote:
> > >
> > > Robert Richter wrote:
> > > > A lookup of a host bridge's corresponding acpi device (struct
> > > > acpi_device) is not possible, for example:
> > > >
> > > >       adev = ACPI_COMPANION(&host_bridge->dev);
> > > >
> > > > This could be useful to find a host bridge's fwnode handle and to
> > > > determine and call additional host bridge ACPI parameters and methods
> > > > such as HID/CID or _UID.
> > >
> > > When is this explicitly needed. "Could be useful" is interesting, but it
> > > needs to have a practical need.
> > 
> > It is needed and it is present on x86 AFAICS (see my last reply in this thread).
> > 
> > This seems to be addressing an ARM64-specific issue.
> > 
> 
> Ah, ok, thanks for pointing that out.

No, it is x86. And true, it is set. So this series is actually working
without this patch. It can be dropped.

Now, I just checked my logs. The reason I was adding this is that
during code development I modified the code to have bridge->dev.parent
set. Then, the fwnode is not linked. I later dropped that change but
kept this patch.

Thanks for catching this.

-Robert