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

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Date:   Tue, 18 Jan 2022 14:53:34 -0500
From:   Sean Anderson <sean.anderson@...o.com>
To:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Baruch Siach <baruch@...s.co.il>
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 Thinh,

On 1/18/22 2:46 PM, Thinh Nguyen wrote:
> 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).

Can you explain your situation a bit more? I'm not sure how you can
access a device tree property but not add a fixed-rate clock.

--Sean