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Date:   Thu, 21 May 2020 01:07:14 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Jun Li <jun.li@....com>, Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Felipe Balbi <balbi@...nel.org>,
        Jun Li <lijun.kernel@...il.com>
CC:     John Stultz <john.stultz@...aro.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Yu Chen <chenyu56@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        ShuFan Lee <shufan_lee@...htek.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Jack Pham <jackp@...eaurora.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Peter Chen <peter.chen@....com>
Subject: Re: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct cleared by
 device controller

Jun Li wrote:
> Hi
>
>> -----Original Message-----
>> From: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
>> Sent: 2020年5月19日 14:46
>> To: Jun Li <jun.li@....com>; Felipe Balbi <balbi@...nel.org>; Jun Li
>> <lijun.kernel@...il.com>
>> Cc: John Stultz <john.stultz@...aro.org>; lkml <linux-kernel@...r.kernel.org>; Yu
>> Chen <chenyu56@...wei.com>; Greg Kroah-Hartman <gregkh@...uxfoundation.org>; Rob
>> Herring <robh+dt@...nel.org>; Mark Rutland <mark.rutland@....com>; ShuFan Lee
>> <shufan_lee@...htek.com>; Heikki Krogerus <heikki.krogerus@...ux.intel.com>;
>> Suzuki K Poulose <suzuki.poulose@....com>; Chunfeng Yun
>> <chunfeng.yun@...iatek.com>; Hans de Goede <hdegoede@...hat.com>; Andy Shevchenko
>> <andy.shevchenko@...il.com>; Valentin Schneider <valentin.schneider@....com>;
>> Jack Pham <jackp@...eaurora.org>; Linux USB List <linux-usb@...r.kernel.org>; open
>> list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS <devicetree@...r.kernel.org>;
>> Peter Chen <peter.chen@....com>
>> Subject: Re: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct cleared by device
>> controller
>>
>> Thinh Nguyen wrote:
>>> Jun Li wrote:
>>>>> -----Original Message-----
>>>>> From: Felipe Balbi <balbif@...il.com> On Behalf Of Felipe Balbi
>>>>> Sent: 2020年5月16日 19:57
>>>>> To: Jun Li <jun.li@....com>; Thinh Nguyen
>>>>> <Thinh.Nguyen@...opsys.com>; Jun Li <lijun.kernel@...il.com>
>>>>> Cc: John Stultz <john.stultz@...aro.org>; lkml
>>>>> <linux-kernel@...r.kernel.org>; Yu Chen <chenyu56@...wei.com>; Greg
>>>>> Kroah-Hartman <gregkh@...uxfoundation.org>; Rob Herring
>>>>> <robh+dt@...nel.org>; Mark Rutland <mark.rutland@....com>; ShuFan
>>>>> Lee <shufan_lee@...htek.com>; Heikki Krogerus
>>>>> <heikki.krogerus@...ux.intel.com>;
>>>>> Suzuki K Poulose <suzuki.poulose@....com>; Chunfeng Yun
>>>>> <chunfeng.yun@...iatek.com>; Hans de Goede <hdegoede@...hat.com>;
>>>>> Andy Shevchenko <andy.shevchenko@...il.com>; Valentin Schneider
>>>>> <valentin.schneider@....com>; Jack Pham <jackp@...eaurora.org>;
>>>>> Linux USB List <linux-usb@...r.kernel.org>; open list:OPEN FIRMWARE
>>>>> AND FLATTENED DEVICE TREE BINDINGS <devicetree@...r.kernel.org>;
>>>>> Peter Chen <peter.chen@....com>; Thinh Nguyen
>>>>> <Thinh.Nguyen@...opsys.com>
>>>>> Subject: RE: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct
>>>>> cleared by device controller
>>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>> Jun Li <jun.li@....com> writes:
>>>>>>>>> Hi Thinh, could you comment this?
>>>>>>>> You only need to wake up the usb2 phy when issuing the command
>>>>>>>> while running in highspeed or below. If you're running in SS or
>>>>>>>> higher, internally the controller does it for you for usb3 phy.
>>>>>>>> In Jun's case, it seems like it takes longer for his phy to wake up.
>>>>>>>>
>>>>>>>> IMO, in this case, I think it's fine to increase the command timeout.
>>>>>>> Is there an upper limit to this? Is 32k clock the slowest that can
>>>>>>> be fed to the PHY as a suspend clock?
>>>>>> Yes, 32K clock is the slowest, Per DWC3 document on Power Down
>>>>>> Scale (bits 31:19 of GCTL):
>>>>>>
>>>>>> "Power Down Scale (PwrDnScale)
>>>>>> The USB3 suspend_clk input replaces pipe3_rx_pclk as a clock source
>>>>>> to a small part of the USB3 controller that operates when the SS
>>>>>> PHY is in its lowest power (P3) state, and therefore does not provide a clock.
>>>>>> The Power Down Scale field specifies how many suspend_clk periods
>>>>>> fit into a 16 kHz clock period. When performing the division, round
>>>>>> up the remainder.
>>>>>> For example, when using an 8-bit/16-bit/32-bit PHY and 25-MHz
>>>>>> Suspend clock, Power Down Scale = 25000 kHz/16 kHz = 13'd1563
>>>>>> (rounder up)
>>>>>> Note:
>>>>>> - Minimum Suspend clock frequency is 32 kHz
>>>>>> - Maximum Suspend clock frequency is 125 MHz"
>>>>> Cool, now do we have an upper bound for how many clock cycles it
>>>>> takes to wake up the PHY?
>>>> My understanding is this ep command does not wake up the SS PHY, the
>>>> SS PHY still stays at P3 when execute this ep command. The time
>>>> required here is to wait controller complete something for this ep
>>>> command with 32K clock.
>>> Sorry I made a mistake. You're right. Just checked with one of the RTL
>>> engineers, and it doesn't need to wake up the phy. However, if it is
>>> eSS speed, it may take longer time as the command may be completing
>>> with the suspend clock.
>>>
>> What's the value for GCTL[7:6]?
> 2'b00
>
> Thanks
> Li Jun

(Sorry for the delay reply)

If it's 0, then the ram clock should be the same as the bus_clk, which 
is odd since you mentioned that the suspend_clk is used instead while in P3.

Anyway, I was looking for a way maybe to improve the speed during 
issuing a command. One way is to set GUSB3PIPECTL[17]=0, and it should 
wakeup the phy anytime. I think Felipe suggested it. It's odd that it 
doesn't work for you. I don't have other ideas beside increasing the 
command timeout.

Thanks,
Thinh

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