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From:   Jun Li <lijun.kernel@gmail.com>
Date:   Mon, 17 Jan 2022 20:30:03 +0800
Message-ID: <CAKgpwJUMXk--4EaYOxAAtLJT85mDHRHMihr6n7y1HECN+gmBBw@mail.gmail.com>
Subject: Re: [PATCH 0/6] usb: dwc3: Calculate REFCLKPER et. al. from reference clock
To:     Sean Anderson <sean.anderson@seco.com>, Li Jun <jun.li@nxp.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux USB List <linux-usb@vger.kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        Robert Hancock <robert.hancock@calian.com>,
        Baruch Siach <baruch@tkos.co.il>,
        Felipe Balbi <balbi@kernel.org>,
        Balaji Prakash J <bjagadee@codeaurora.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Michal Simek <michal.simek@xilinx.com>,
        Rob Herring <robh+dt@kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-arm-msm@vger.kernel.org
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Sean Anderson <sean.anderson@seco.com> =E4=BA=8E2022=E5=B9=B41=E6=9C=8815=
=E6=97=A5=E5=91=A8=E5=85=AD 10:11=E5=86=99=E9=81=93=EF=BC=9A
>
> This is a rework of patches 3-5 of [1]. It attempts to correctly program
> REFCLKPER and REFCLK_FLADJ based on the reference clock frequency. Since
> we no longer need a special property duplicating this configuration,
> snps,ref-clock-period-ns is deprecated.
>
> Please test this! Patches 3/4 in this series have the effect of
> programming REFCLKPER and REFCLK_FLADJ on boards which already configure
> the "ref" clock. I have build tested, but not much else.

DWC3 databook states a *condition* for program those settings:

This field must be programmed to a non-zero value only if
GFLADJ_REFCLK_LPM_SEL is set to '1' or GCTL.SOFITPSYNC is set to '1'.
The value is derived as follows:
FLADJ_REF_CLK_FLADJ=3D((125000/ref_clk_period_integer)-(125000/ref_clk_peri=
od))
* ref_clk_period where
=E2=96=A0 the ref_clk_period_integer is the integer value of the ref_clk
period got by truncating the decimal (fractional) value that is
programmed in the GUCTL.REF_CLK_PERIOD field.
=E2=96=A0 the ref_clk_period is the ref_clk period including the fractional=
 value.

So you may need a condition check, with that, only required users
are effected even with "ref" clock specified.

Li Jun

>
> [1] https://lore.kernel.org/linux-usb/20220114044230.2677283-1-robert.han=
cock@calian.com/
>
>
> Sean Anderson (6):
>   dt-bindings: usb: dwc3: Deprecate snps,ref-clock-period-ns
>   usb: dwc3: Get clocks individually
>   usb: dwc3: Calculate REFCLKPER based on reference clock
>   usb: dwc3: Handle fractional reference clocks
>   arm64: dts: zynqmp: Move USB clocks to dwc3 node
>   arm64: dts: ipq6018: Use reference clock to set dwc3 period
>
>  .../devicetree/bindings/usb/snps,dwc3.yaml    |  7 +-
>  arch/arm64/boot/dts/qcom/ipq6018.dtsi         |  3 +-
>  .../arm64/boot/dts/xilinx/zynqmp-clk-ccf.dtsi |  4 +-
>  arch/arm64/boot/dts/xilinx/zynqmp.dtsi        |  4 +-
>  drivers/usb/dwc3/core.c                       | 98 ++++++++++++++++---
>  drivers/usb/dwc3/core.h                       |  6 +-
>  6 files changed, 98 insertions(+), 24 deletions(-)
>
> --
> 2.25.1
>