linux-kernel - Re: [PATCH 0/6] usb: dwc3: Calculate REFCLKPER et. al. from reference clock

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Date:   Tue, 18 Jan 2022 19:46:19 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Baruch Siach <baruch@...s.co.il>,
        Sean Anderson <sean.anderson@...o.com>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Robert Hancock <robert.hancock@...ian.com>,
        Felipe Balbi <balbi@...nel.org>,
        Balaji Prakash J <bjagadee@...eaurora.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Michal Simek <michal.simek@...inx.com>,
        Rob Herring <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH 0/6] usb: dwc3: Calculate REFCLKPER et. al. from reference
 clock

Hi Sean,

Baruch Siach wrote:
> Hi Sean, Thinh,
> 
> On Fri, Jan 14 2022, Sean Anderson wrote:
>> 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.
>>
>> [1] https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/20220114044230.2677283-1-robert.hancock@calian.com/__;!!A4F2R9G_pg!M3zKxDZC9a_etqzXo7GSEMTHRWfc1wR_84wwM4-fShiA35CsGcxcTEffHPbprbdC4d2R$ 
> 
> Thinh, you suggested the dedicated DT property for the reference clock:
> 
>   https://urldefense.com/v3/__https://lore.kernel.org/all/d5acb192-80b9-36f7-43f5-81f21c4e6ba0@synopsys.com/__;!!A4F2R9G_pg!M3zKxDZC9a_etqzXo7GSEMTHRWfc1wR_84wwM4-fShiA35CsGcxcTEffHPbprbpOFmvX$ 
> 
> Can you comment on this series?
> 

Unless there's a good way to pass this information for PCI devices, my
opinion hasn't changed. (Btw, I don't think creating a dummy clock
provider and its dummy ops is a good solution as seems to complicate and
bloat the PCI glue drivers).

Please help come up with a solution before deprecating the ref clock
property.

Thanks,
Thinh

> 
>> 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(-)
> 
>