linux-kernel - RE: [EXT] Re: [PATCH v1] usb: dwc3: remove the call trace of USBx

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Date:   Thu, 15 Aug 2019 04:18:01 +0000
From:   Yinbo Zhu <yinbo.zhu@....com>
To:     Felipe Balbi <balbi@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
CC:     Xiaobo Xie <xiaobo.xie@....com>, Jiafei Pan <jiafei.pan@....com>,
        Ran Wang <ran.wang_1@....com>
Subject: RE: [EXT] Re: [PATCH v1] usb: dwc3: remove the call trace of
 USBx_GFLADJ



> -----Original Message-----
> From: Felipe Balbi [mailto:balbi@...nel.org]
> Sent: 2019年8月12日 13:27
> To: Yinbo Zhu <yinbo.zhu@....com>; Greg Kroah-Hartman
> <gregkh@...uxfoundation.org>; linux-usb@...r.kernel.org; open list
> <linux-kernel@...r.kernel.org>
> Cc: Xiaobo Xie <xiaobo.xie@....com>; Jiafei Pan <jiafei.pan@....com>; Ran
> Wang <ran.wang_1@....com>
> Subject: RE: [EXT] Re: [PATCH v1] usb: dwc3: remove the call trace of
> USBx_GFLADJ
> 
> Caution: EXT Email
> 
> Hi,
> 
> Yinbo Zhu <yinbo.zhu@....com> writes:
> >> > diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> >> > index
> >> > 98bce85c29d0..a133d8490322 100644
> >> > --- a/drivers/usb/dwc3/core.c
> >> > +++ b/drivers/usb/dwc3/core.c
> >> > @@ -300,8 +300,7 @@ static void dwc3_frame_length_adjustment(struct
> >> > dwc3 *dwc)
> >> >
> >> >       reg = dwc3_readl(dwc->regs, DWC3_GFLADJ);
> >> >       dft = reg & DWC3_GFLADJ_30MHZ_MASK;
> >> > -     if (!dev_WARN_ONCE(dwc->dev, dft == dwc->fladj,
> >> > -         "request value same as default, ignoring\n")) {
> >> > +     if (dft != dwc->fladj) {
> >>
> >> if the value isn't different, why do you want to change it?
> >>
> >> --
> >> Balbi
> > Hi Balbi,
> >
> > I don't change any value. I was remove that call trace.
> 
> Sure you do. The splat only shows when you request a FLADJ value that's the
> same as the one already in the register. The reason you see the splat is because
> your requested value is what's already in the HW.
> 
> So, again, why are you adding this device tree property if the value is already the
> correct one?
> 
> > In addition that GFLADJ_30MHZ value intial value is 0, and it's value
> > must be 0x20, if not, usb will not work.
> 
> it's not zero, otherwise the splat wouldn't trigger. You're requesting the value
> that's already in your register by default.
> 
> --
> Balbi

Hi Balbi,
   
According that rm doc that GFLADJ_30MHZ has a default value is 0x20, when GFLADJ_30MHZ_REG_SEL is 0, this 0x20 is a hard-coded value.
But in fact, that default value is 0, please you note!    
Then according that xhci spec 5.2.4, that register the sixth bit if is 0, then that can support Frame Lenth Timing value.
So set GFLADJ_30MHZ_REG_SEL to 1 for use FLADJ, then I find that it must use 0x20 usb will work well, even thoug xhci can permit GFLADJ_30MHZ use other value
In addition about what you said is about dts patch, and that patch had merged by upstream, patch owner isn't me, 
My patch is only for remove the call-trace, about why remove it commit information has detail introduce please check!

Thanks,
Yinbo.