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

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Message-ID: <bc7732aa-6958-4028-a3b3-a0c2ba3b0252@oss.qualcomm.com>
Date: Sat, 1 Nov 2025 09:08:05 +0530
From: Krishna Chaitanya Chundru <krishna.chundru@....qualcomm.com>
To: Bjorn Helgaas <helgaas@...nel.org>
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 11/1/2025 3:42 AM, Bjorn Helgaas wrote:
> 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.

Hi Bjorn,

As this is just an example, we just added here. In actually use case we 
are free
to add it for any port.

For remaining comments, you are right I didn't notice I am still using 
older one's
I will fix in next series.

- Krishna Chaitanya.

>>    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
>>>