linux-kernel - Re: [PATCH v2 0/7] usb: dwc3: Calculate REFCLKPER et. al. from reference clock

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Date:   Mon, 24 Jan 2022 23:01:44 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Kathiravan Thirumoorthy <quic_kathirav@...cinc.com>,
        Baruch Siach <baruch@...s.co.il>,
        Kathiravan T <kathirav@...eaurora.org>
CC:     Sean Anderson <sean.anderson@...o.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        Felipe Balbi <balbi@...nel.org>,
        Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Balaji Prakash J <bjagadee@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Robert Hancock <robert.hancock@...ian.com>,
        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 v2 0/7] usb: dwc3: Calculate REFCLKPER et. al. from
 reference clock

Kathiravan Thirumoorthy wrote:
> Hi Baruch,
> 
> On 1/20/2022 3:59 PM, Baruch Siach wrote:
>> Hi Kathiravan,
>>
>> On Thu, Jan 20 2022, Kathiravan T wrote:
>>> On 2022-01-19 23:44, Baruch Siach wrote:
>>>> Hi Sean,
>>>> On Tue, Jan 18 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.
>>>> Tested here on IPQ6010 based system. USB still works. But the with
>>>> "ref"
>>>> clock at 24MHz, period is calculated as 0x29. Previous
>>>> snps,ref-clock-period-ns value used to be 0x32.
>>>> Is that expected?
>>> Yes, it is 0x29 for IPQ60xx based SoCs. In downstream it was wrongly
>>> mentioned
>>> as 0x32, which was corrected recently.
>> Thanks for the update. This needs fixing in upstream kernel. I'll send a
>> patch.
>>
>> For some reason USB appears to work here with both values. Is it because
>> I only use USB2 signals? If this is the case them I can not actually
>> test this series on my system.

The controller uses the GUCTL.REFCLKPER under specific conditions and
settings, and the conditions are different between host mode and device
mode. For example, if you're running as device-mode and not operating in
low power, and or not using periodic endpoints, you're not probably
testing this.

BR,
Thinh


> 
> I could recollect we did see some issue on USB2.0 port as well, but it
> wasn't fatal one. Anyways it is better to test it.
> 
> Thanks,
> 
> Kathiravan T.
> 
>>
>> Thanks,
>> baruch
>>
>>>>> [1]
>>>>> https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/20220114044230.2677283-1-robert.hancock@calian.com/__;!!A4F2R9G_pg!MCqqTGYTR42-4_LUHhrSJjkUOkDZKb795I8lB3PY4dB-kVCBnR9YKucgzrwhlj0tZZm5$
>>>>> Changes in v2:
>>>>> - Document clock members
>>>>> - Also program GFLADJ.240MHZDECR
>>>>> - Don't program GFLADJ if the version is < 2.50a
>>>>> - Add snps,ref-clock-frequency-hz property for ACPI
>>>>> Sean Anderson (7):
>>>>>    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: Program GFLADJ
>>>>>    usb: dwc3: Add snps,ref-clock-frequency-hz property for ACPI
>>>>>    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                       | 112
>>>>> +++++++++++++++---
>>>>>   drivers/usb/dwc3/core.h                       |  17 ++-
>>>>>   6 files changed, 120 insertions(+), 27 deletions(-)
>>