Date:   Wed, 27 Oct 2021 17:31:01 -0400
From:   Jim Quinlan <james.quinlan@...adcom.com>
To:     Rob Herring <robh@...nel.org>
Cc:     Jim Quinlan <jim2101024@...il.com>,
        "open list:PCI NATIVE HOST BRIDGE AND ENDPOINT DRIVERS" 
        <linux-pci@...r.kernel.org>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Mark Brown <broonie@...nel.org>,
        "maintainer:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <bcm-kernel-feedback-list@...adcom.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Saenz Julienne <nsaenzjulienne@...e.de>,
        "moderated list:BROADCOM BCM7XXX ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:BROADCOM BCM2711/BCM2835 ARM ARCHITECTURE" 
        <linux-rpi-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/6] dt-bindings: PCI: Add bindings for Brcmstb EP
 voltage regulators

On Wed, Oct 27, 2021 at 4:54 PM Rob Herring <robh@...nel.org> wrote:
>
> On Tue, Oct 26, 2021 at 4:27 PM Jim Quinlan <james.quinlan@...adcom.com> wrote:
> >
> > On Mon, Oct 25, 2021 at 6:24 PM Rob Herring <robh@...nel.org> wrote:
> > >
> > > On Fri, Oct 22, 2021 at 10:06:54AM -0400, Jim Quinlan wrote:
> > > > Similar to the regulator bindings found in "rockchip-pcie-host.txt", this
> > > > allows optional regulators to be attached and controlled by the PCIe RC
> > > > driver.  That being said, this driver searches in the DT subnode (the EP
> > > > node, eg pci@0,0) for the regulator property.
> > > >
> > > > The use of a regulator property in the pcie EP subnode such as
> > > > "vpcie12v-supply" depends on a pending pullreq to the pci-bus.yaml
> > > > file at
> > > >
> > > > https://github.com/devicetree-org/dt-schema/pull/54
> > > >
> > > > Signed-off-by: Jim Quinlan <jim2101024@...il.com>
> > > > ---
> > > >  .../bindings/pci/brcm,stb-pcie.yaml           | 23 +++++++++++++++++++
> > > >  1 file changed, 23 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
> > > > index b9589a0daa5c..fec13e4f6eda 100644
> > > > --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
> > > > +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
> > > > @@ -154,5 +154,28 @@ examples:
> > > >                                   <0x42000000 0x1 0x80000000 0x3 0x00000000 0x0 0x80000000>;
> > > >                      brcm,enable-ssc;
> > > >                      brcm,scb-sizes =  <0x0000000080000000 0x0000000080000000>;
> > > > +
> > > > +                    /* PCIe bridge */
> > >
> > > More specifically, the root port.
> > >
> > > > +                    pci@0,0 {
> > > > +                            #address-cells = <3>;
> > > > +                            #size-cells = <2>;
> > > > +                            reg = <0x0 0x0 0x0 0x0 0x0>;
> > > > +                            device_type = "pci";
> > > > +                            ranges;
> > > > +
> > > > +                            /* PCIe endpoint */
> > > > +                            pci@0,0 {
> > > > +                                    device_type = "pci";
> > >
> > > This means this device is a PCI bridge which wouldn't typically be the
> > > endpoint. Is that intended?
> > Hi Rob,
> >
> > I'm not sure I understand what you are saying --  do you want the
> > innermost node to be named something like ep-pci@0,0, and its
> > containing node pci-bridge@0,0?   Or, more likely, I'm missing the
> > point.  If my DT subtree is this
>
> I'm confused as to how a bridge is the endpoint. If it is a bridge
> (which 'device_type = "pci"' means it is), then there should be
> another PCI device under it. That may or may not have a DT node.

I did not know that device_type="pci" implies that it must be a
bridge;  [1] says "device_type" is deprecated  for PCI and [2] defers
to Open Firmware EEE 1275, which is not free AFAICT. Do you have
better URLs that describe this?  At any rate, I will remove the
device_type="pci" from the innermost DT node, and resubmit.

>
> > pcie@...0000 {
> >     compatible = "brcm,bcm7278-pcie";
> >     ....
> >     pci-bridge@0,0 {
> >         reg = <0x0 0x0 0x0 0x0 0x0>; /* bus 0 */
> >         .....
> >         pci-ep@0,0,0 {
> >             reg = <0x10000 0x0 0x0 0x0 0x0>;  /* bus 1 */
> >             vpcie3v3-supply = <&vreg8>;
> >             ...
> >         }
> >     }
> > }
> >
> > then the of_nodes appear to align correctly with the devices:
> >
> > $ cd /sys/devices/platform/
> > $ cat 8b10000.pcie/of_node/name
> > pcie
> > $ cat 8b10000.pcie/pci0000:00/0000:00:00.0/of_node
> > pci-bridge
> > $ cat 8b10000.pcie/pci0000:00/0000:00:00.0/0000:01:00.0/of_node/name
> > pci-ep
>
> What does 'lspci -tv' show?

$ lspci -tv
-+-[0000:01]---00.0  Intel Corporation Wireless 7260
  \-[0000:00]---00.0  Broadcom Inc. and subsidiaries Device 7278


>
> >
> > and the EP device works of course.  I've even printed out the
> > device_node structure in the EP driver's probe and it is as expected.
> > I've noticed that examples such as
> > "arch/arm64/boot/dts/nvidia/tegra186.dtsi" have the EP node (eg
> > pci@1,0) directly under the
> > host bridge DT node (pcie@...03000).  I did try doing that, but the EP
> > device's probe is given a NUL device_node pointer.
>
> If you want a complex example I know that's right, then see hikey970.

Thanks, will look.

Jim

[1] https://buildmedia.readthedocs.org/media/pdf/devicetree-specification/latest/devicetree-specification.pdf
[2] https://www.openfirmware.info/data/docs/bus.pci.pdf
>
> Rob

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