Re: [PATCH v3 1/3] dt-bindings: phy: qcom,qmp: Add PCIe qcom,refclk-always-on property

Manivannan Sadhasivam
2023-12-01T11:10:53Z

On Fri, Dec 01, 2023 at 09:01:43AM +0100, Krzysztof Kozlowski wrote:
> On 01/12/2023 07:07, Manivannan Sadhasivam wrote:
> > On Tue, Nov 28, 2023 at 02:49:18PM +0530, Krishna Chaitanya Chundru wrote:
> >>
> >> On 11/28/2023 2:26 PM, Krzysztof Kozlowski wrote:
> >>> On 27/11/2023 13:13, Krishna chaitanya chundru wrote:
> >>>> Document qcom,refclk-always-on property which is needed in some platforms
> >>>> to supply refclk even in PCIe low power states.
> >>>>
> >>>> Signed-off-by: Krishna chaitanya chundru <quic_krichai@quicinc.com>
> >>>> ---
> >>>> .../devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml | 7 +++++++
> >>>> 1 file changed, 7 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
> >>>> index 2c3d6553a7ba..c747c9f35795 100644
> >>>> --- a/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
> >>>> +++ b/Documentation/devicetree/bindings/phy/qcom,sc8280xp-qmp-pcie-phy.yaml
> >>>> @@ -93,6 +93,13 @@ properties:
> >>>> "#phy-cells":
> >>>> const: 0
> >>>> + qcom,refclk-always-on:
> >>>> + type: boolean
> >>>> + description: In some platform where PCIe switch is connected, pcie switch due to some design
> >>> You received a comment to use proper wrapping: 80. Please implement it.
> >> I will update this.
> >>>> + limitation fails to propage clkreq signal to the host and due to that host will not send
> >>>> + refclk, which results in linkdown in L1.2 or L1.1 exit initiated by EP.
> >>>> + This property if set keeps refclk always on even in Low power states.
> >>> The property name suggests that's the state of hardware - refclk is
> >>> always on. Description suggests you want to instruct OS to do something.
> >>>
> >>> Again, third time (once from Bjorn, once from Dmitry), rephrase property
> >>> name and description to describe the hardware issue. I see description
> >>> improved, but not the property name. Again in the end of description you
> >>
> >> Both bjorn and Dmitry gave comments to change the description only, and not
> >> the property name,
> >>
> >> correct if I am wrong.
> >>
> >>> say what Linux should do. Bindings do not describe Linux OS.
> >>
> >> I will remove the last line in the next patch.
> >>
> >
> > You should name the property as, "qcom,keep-refclk-always-on"
>
> Keep the clock by who? By driver? Then not, property should describe
> physical phenomena or hardware issue being fixed here, not what driver
> should do.
>

This property indeed fixes the hardware issue (though in board level) and I see
a plenty of properties similar to this one instructing the OS to keep some
resource ON to workaround hardware issues. So they are all wrong?

- Mani

>
> Best regards,
> Krzysztof
>

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