Re: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct cleared by device controller

[Thinh Nguyen]

Jun Li wrote:
> Hi
>
>> -----Original Message-----
>> From: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
>> Sent: 2020å5æ19æ 14:46
>> To: Jun Li <jun.li@xxxxxxx>; Felipe Balbi <balbi@xxxxxxxxxx>; Jun Li
>> <lijun.kernel@xxxxxxxxx>
>> Cc: John Stultz <john.stultz@xxxxxxxxxx>; lkml <linux-kernel@xxxxxxxxxxxxxxx>; Yu
>> Chen <chenyu56@xxxxxxxxxx>; Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Rob
>> Herring <robh+dt@xxxxxxxxxx>; Mark Rutland <mark.rutland@xxxxxxx>; ShuFan Lee
>> <shufan_lee@xxxxxxxxxxx>; Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>;
>> Suzuki K Poulose <suzuki.poulose@xxxxxxx>; Chunfeng Yun
>> <chunfeng.yun@xxxxxxxxxxxx>; Hans de Goede <hdegoede@xxxxxxxxxx>; Andy Shevchenko
>> <andy.shevchenko@xxxxxxxxx>; Valentin Schneider <valentin.schneider@xxxxxxx>;
>> Jack Pham <jackp@xxxxxxxxxxxxxx>; Linux USB List <linux-usb@xxxxxxxxxxxxxxx>; open
>> list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS <devicetree@xxxxxxxxxxxxxxx>;
>> Peter Chen <peter.chen@xxxxxxx>
>> 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@xxxxxxxxx> On Behalf Of Felipe Balbi
>>>>> Sent: 2020å5æ16æ 19:57
>>>>> To: Jun Li <jun.li@xxxxxxx>; Thinh Nguyen
>>>>> <Thinh.Nguyen@xxxxxxxxxxxx>; Jun Li <lijun.kernel@xxxxxxxxx>
>>>>> Cc: John Stultz <john.stultz@xxxxxxxxxx>; lkml
>>>>> <linux-kernel@xxxxxxxxxxxxxxx>; Yu Chen <chenyu56@xxxxxxxxxx>; Greg
>>>>> Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>; Rob Herring
>>>>> <robh+dt@xxxxxxxxxx>; Mark Rutland <mark.rutland@xxxxxxx>; ShuFan
>>>>> Lee <shufan_lee@xxxxxxxxxxx>; Heikki Krogerus
>>>>> <heikki.krogerus@xxxxxxxxxxxxxxx>;
>>>>> Suzuki K Poulose <suzuki.poulose@xxxxxxx>; Chunfeng Yun
>>>>> <chunfeng.yun@xxxxxxxxxxxx>; Hans de Goede <hdegoede@xxxxxxxxxx>;
>>>>> Andy Shevchenko <andy.shevchenko@xxxxxxxxx>; Valentin Schneider
>>>>> <valentin.schneider@xxxxxxx>; Jack Pham <jackp@xxxxxxxxxxxxxx>;
>>>>> Linux USB List <linux-usb@xxxxxxxxxxxxxxx>; open list:OPEN FIRMWARE
>>>>> AND FLATTENED DEVICE TREE BINDINGS <devicetree@xxxxxxxxxxxxxxx>;
>>>>> Peter Chen <peter.chen@xxxxxxx>; Thinh Nguyen
>>>>> <Thinh.Nguyen@xxxxxxxxxxxx>
>>>>> Subject: RE: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct
>>>>> cleared by device controller
>>>>>
>>>>>
>>>>> Hi,
>>>>>
>>>>> Jun Li <jun.li@xxxxxxx> 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