linux-kernel - Re: [PATCH v8 1/7] dt-bindings: PCI: Add binding for Toshiba TC9563 PCIe switch

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Message-ID: <20251031221238.GA1711866@bhelgaas>
Date: Fri, 31 Oct 2025 17:12:38 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Jingoo Han <jingoohan1@...il.com>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	cros-qcom-dts-watchers@...omium.org, linux-pci@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v8 1/7] dt-bindings: PCI: Add binding for Toshiba TC9563
 PCIe switch

On Fri, Oct 31, 2025 at 05:00:13PM -0500, Bjorn Helgaas wrote:
> On Fri, Oct 31, 2025 at 04:41:58PM +0530, Krishna Chaitanya Chundru wrote:
> > Add a device tree binding for the Toshiba TC9563 PCIe switch, which
> > provides an Ethernet MAC integrated to the 3rd downstream port and
> > two downstream PCIe ports.

> > +                pcie@1,0 {
> > +                    compatible = "pciclass,0604";
> > +                    reg = <0x20800 0x0 0x0 0x0 0x0>;
> > +                    #address-cells = <3>;
> > +                    #size-cells = <2>;
> > +                    device_type = "pci";
> > +                    ranges;
> > +                    bus-range = <0x03 0xff>;
> > +
> > +                    toshiba,no-dfe-support;
> 
> IIUC, there are two downstream ports available for external devices,
> and pcie@1,0 is one of them.
> 
>   1) Putting "toshiba,no-dfe-support" in the pcie@1,0 stanza suggests
>   that it only applies to that port.
> 
>   But from tc9563_pwrctrl_disable_dfe() in "[PATCH v8 6/7] PCI:
>   pwrctrl: Add power control driver for tc9563", it looks like it's
>   applied to the upstream port and both downstream ports.  So I guess
>   my question is putting "toshiba,no-dfe-support" in just one
>   downstream port is the right place for it.

Oh, I see, never mind.  You keep track of ->disable_dfe on a per-port
basis, so each port has the *possibility* of using it, and you skip
programming it if the port doesn't have it.

I would assume the two downstream ports for external devices would be
identical, so I do still wonder why you would specify this for only
one of them.

>   2) I see a lookup of "qcom,no-dfe-support" in [PATCH v8 6/7] PCI:
>   pwrctrl: Add power control driver for tc9563; is that supposed to
>   match this "toshiba,no-dfe-support"?
> 
> > +                };
> > +
> > +                pcie@2,0 {
> > +                    compatible = "pciclass,0604";
> > +                    reg = <0x21000 0x0 0x0 0x0 0x0>;
> > +                    #address-cells = <3>;
> > +                    #size-cells = <2>;
> > +                    device_type = "pci";
> > +                    ranges;
> > +                    bus-range = <0x04 0xff>;
> > +                };
> > +
> > +                pcie@3,0 {
> > +                    compatible = "pciclass,0604";
> > +                    reg = <0x21800 0x0 0x0 0x0 0x0>;
> > +                    #address-cells = <3>;
> > +                    #size-cells = <2>;
> > +                    device_type = "pci";
> > +                    ranges;
> > +                    bus-range = <0x05 0xff>;
> > +
> > +                    toshiba,tx-amplitude-microvolt = <10>;

Same question here about whether "toshiba,tx-amplitude-microvolt" is
supposed to match the "qcom,tx-amplitude-microvolt" in the driver.

> > +                    ethernet@0,0 {
> > +                        reg = <0x50000 0x0 0x0 0x0 0x0>;
> > +                    };
> > +
> > +                    ethernet@0,1 {
> > +                        reg = <0x50100 0x0 0x0 0x0 0x0>;
> > +                    };
> > +                };
> > +            };
> > +        };
> > +    };
> > 
> > -- 
> > 2.34.1
> >