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

[Jun Li]

Hi

> -----Original Message-----
> From: Thinh Nguyen <thinh.ngu...@synopsys.com>
> Sent: 2020年5月19日 14:46
> To: Jun Li <jun...@nxp.com>; Felipe Balbi <ba...@kernel.org>; Jun Li
> <lijun.ker...@gmail.com>
> Cc: John Stultz <john.stu...@linaro.org>; lkml 
> <linux-kernel@vger.kernel.org>; Yu
> Chen <cheny...@huawei.com>; Greg Kroah-Hartman <gre...@linuxfoundation.org>; 
> Rob
> Herring <robh...@kernel.org>; Mark Rutland <mark.rutl...@arm.com>; ShuFan Lee
> <shufan_...@richtek.com>; Heikki Krogerus <heikki.kroge...@linux.intel.com>;
> Suzuki K Poulose <suzuki.poul...@arm.com>; Chunfeng Yun
> <chunfeng....@mediatek.com>; Hans de Goede <hdego...@redhat.com>; Andy 
> Shevchenko
> <andy.shevche...@gmail.com>; Valentin Schneider <valentin.schnei...@arm.com>;
> Jack Pham <ja...@codeaurora.org>; Linux USB List <linux-...@vger.kernel.org>; 
> open
> list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS 
> <devicet...@vger.kernel.org>;
> Peter Chen <peter.c...@nxp.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 <bal...@gmail.com> On Behalf Of Felipe Balbi
> >>> Sent: 2020年5月16日 19:57
> >>> To: Jun Li <jun...@nxp.com>; Thinh Nguyen
> >>> <thinh.ngu...@synopsys.com>; Jun Li <lijun.ker...@gmail.com>
> >>> Cc: John Stultz <john.stu...@linaro.org>; lkml
> >>> <linux-kernel@vger.kernel.org>; Yu Chen <cheny...@huawei.com>; Greg
> >>> Kroah-Hartman <gre...@linuxfoundation.org>; Rob Herring
> >>> <robh...@kernel.org>; Mark Rutland <mark.rutl...@arm.com>; ShuFan
> >>> Lee <shufan_...@richtek.com>; Heikki Krogerus
> >>> <heikki.kroge...@linux.intel.com>;
> >>> Suzuki K Poulose <suzuki.poul...@arm.com>; Chunfeng Yun
> >>> <chunfeng....@mediatek.com>; Hans de Goede <hdego...@redhat.com>;
> >>> Andy Shevchenko <andy.shevche...@gmail.com>; Valentin Schneider
> >>> <valentin.schnei...@arm.com>; Jack Pham <ja...@codeaurora.org>;
> >>> Linux USB List <linux-...@vger.kernel.org>; open list:OPEN FIRMWARE
> >>> AND FLATTENED DEVICE TREE BINDINGS <devicet...@vger.kernel.org>;
> >>> Peter Chen <peter.c...@nxp.com>; Thinh Nguyen
> >>> <thinh.ngu...@synopsys.com>
> >>> Subject: RE: [PATCH v4 3/9] usb: dwc3: Increase timeout for CmdAct
> >>> cleared by device controller
> >>>
> >>>
> >>> Hi,
> >>>
> >>> Jun Li <jun...@nxp.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
> 
> BR,
> Thinh