Re: [PATCH v4 2/6] dt-bindings: PCI: Add bindings for Brcmstb endpoint device voltage regulators

From: Rob Herring <robh@kernel.org>
To: Jim Quinlan <jim2101024@gmail.com>
Cc: Mark Brown <broonie@kernel.org>,
	linux-pci <linux-pci@vger.kernel.org>,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
	bcm-kernel-feedback-list <bcm-kernel-feedback-list@broadcom.com>,
	Jim Quinlan <james.quinlan@broadcom.com>,
	Florian Fainelli <f.fainelli@gmail.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
	<linux-rpi-kernel@lists.infradead.org>,
	"moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
	<linux-arm-kernel@lists.infradead.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
	<devicetree@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 2/6] dt-bindings: PCI: Add bindings for Brcmstb endpoint device voltage regulators
Date: Thu, 8 Apr 2021 11:20:16 -0500	[thread overview]
Message-ID: <20210408162016.GA1556444@robh.at.kernel.org> (raw)
In-Reply-To: <CANCKTBv63b4bGepZbDp1wmFrOeddiDikoXbheMjHhbguAbR2sA@mail.gmail.com>

On Tue, Apr 06, 2021 at 02:25:49PM -0400, Jim Quinlan wrote:
> On Tue, Apr 6, 2021 at 1:32 PM Mark Brown <broonie@kernel.org> wrote:
> >
> > On Tue, Apr 06, 2021 at 01:26:51PM -0400, Jim Quinlan wrote:
> > > On Tue, Apr 6, 2021 at 12:47 PM Mark Brown <broonie@kernel.org> wrote:
> >
> > > > No great problem with having these in the controller node (assming it
> > > > accurately describes the hardware) but I do think we ought to also be
> > > > able to describe these per slot.

PCIe is effectively point to point, so there's only 1 slot unless 
there's a PCIe switch in the middle. If that's the case, then it's all 
more complicated.

> > > Can you explain what you think that would look like in the DT?
> >
> > I *think* that's just some properties on the nodes for the endpoints,
> > note that the driver could just ignore them for now.  Not sure where or
> > if we document any extensions but child nodes are in section 4 of the
> > v2.1 PCI bus binding.
> 
> Hi Mark,
> 
> I'm a little confused -- here is how I remember the chronology of the
> "DT bindings" commit reviews, please correct me if I'm wrong:
> 
> o JimQ submitted a pullreq for using voltage regulators in the same
> style as the existing "rockport" PCIe driver.
> o After some deliberation, RobH preferred that the voltage regulators
> should go into the PCIe subnode device's DT node.

IIRC, that's because you said there isn't a standard slot.

> o JimQ put the voltage regulators in the subnode device's DT node.
> o MarkB didn't like the fact that the code did a global search for the
> regulator since it could not provide the owning struct device* handle.
> o RobH relented, and said that if it is just two specific and standard
> voltage regulators, perhaps they can go in the parent DT node after
> all.
> o JimQ put the regulators back in the PCIe node.
> o MarkB now wants the regulators to go back into the child node again?
> 
> Folks, please advise.
> 
> Regards,
> Jim Quinlan
> Broadcom STB