[U-Boot] [RESEND PATCH 3/5] usb: host: dwc2: force reset assert

[Patrick DELAUNAY]

Hi,

> 
> On 11/8/19 10:53 AM, Patrick DELAUNAY wrote:
> > Hi,
> 
> Hi,
> 
> [...]
> 
> >>>>> diff --git a/drivers/usb/host/dwc2.c b/drivers/usb/host/dwc2.c
> >>>>> index
> >>>>> 51023b0c2c..3086411fc4 100644
> >>>>> --- a/drivers/usb/host/dwc2.c
> >>>>> +++ b/drivers/usb/host/dwc2.c
> >>>>> @@ -1149,6 +1149,8 @@ static int dwc2_reset(struct udevice *dev)
> >>>>>  			return ret;
> >>>>>  	}
> >>>>>
> >>>>> +	reset_assert_bulk(&priv->resets);
> >>>>> +	udelay(2);
> >>>>
> >>>> Why is there a 2 uS delay ?
> >>>
> >>> I think: no real reason to have 2 us....
> >>>
> >>> It was jus a reasonable time to be sure that the device reset is
> >>> correctly performed, the reset signal is propagated....
> >>>
> >>> but perhaps that no delay is working...
> >>> I can test without delay if you prefer...
> >>>
> >>> PS: I use the same value than DWC2 gadget driver:
> >>>        Added by my commit c2c74f97afff
> >>
> >> Isn't there a way to poll the IP to determine whether the reset completed ?
> >
> > It is HW IP reset, the complete state is not available for stm32mp1 reset
> controller (RCC).
> > And the need reset duration of depends on each IP (can't be handle in reset u-
> class).
> 
> If it's a SoC specific delay, it should be in the reset driver.
> 
> > I check with DWC2 OTG IP expert, and we found in
> > DWC_otg_databook_3.30a.pdf
> >
> > t_rst: DWC_otg PHY clock domain reset and AHB hclk domain reset over lap
> time
> >         (a minimum of 12 cycles of the slowest clock is recommended.)
> >
> > In our board, we have 209MHz for AHB frequency... USB phy clock is
> > 48MHz So freq12 cycles is MIN(57ns,  250ns) < 1us.
> >
> > The 2us value seens a over protection.
> >
> > I will reduce it to 1us in V2 and I will add comments for.
> 
> Well, why don't you put this into the reset driver ? Seems to be a more fitting place
> for this. I don't think every single SoC has the same clock settings.

Ok, I will remove the delay in driver.

Patrick