On Mon, Mar 17, 2025, Mike Looijmans wrote:
> On 14-03-2025 22:14, Thinh Nguyen wrote:
> > On Fri, Mar 14, 2025, Mike Looijmans wrote:
> > > Set the gpio to "high" on acquisition, instead of acquiring it in low
> > > state and then immediately setting it high again. This prevents a
> > > short "spike" on the reset signal.
> > How does this affect the current programming flow beside preventing a
> > spike to the reset signal?
>
> I don't understand your question. What "programming flow" are you referring
> to?
It's not obvious to me if this is an error in Xilinx documentation, the
driver issue, or whether this is found through experiment. Since I don't
have the info of this platform, it would help to know where the source
of error is so we can document this in the code or change-log.
>
> The reset sequence was just plain wrong, the issue is almost the same as the
Do we need a fix tag and add to stable then?
> one described in this commit:
> e0183b974d30 "net: mdiobus: Prevent spike on MDIO bus reset signal"
>
> Note that I see this high-low-high-low double reset toggle in many Xilinx
> software drivers, they seem to teach that at the Xilinx academy or so.
>
>
> > > Signed-off-by: Mike Looijmans <mike.looijmans@xxxxxxxx>
> > > ---
> > >
> > > drivers/usb/dwc3/dwc3-xilinx.c | 3 +--
> > > 1 file changed, 1 insertion(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/usb/dwc3/dwc3-xilinx.c b/drivers/usb/dwc3/dwc3-xilinx.c
> > > index a33a42ba0249..a159a511483b 100644
> > > --- a/drivers/usb/dwc3/dwc3-xilinx.c
> > > +++ b/drivers/usb/dwc3/dwc3-xilinx.c
> > > @@ -207,7 +207,7 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
> > > skip_usb3_phy:
> > > /* ulpi reset via gpio-modepin or gpio-framework driver */
> > > - reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> > > + reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> > > if (IS_ERR(reset_gpio)) {
> > > return dev_err_probe(dev, PTR_ERR(reset_gpio),
> > > "Failed to request reset GPIO\n");
> > > @@ -215,7 +215,6 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
> > > if (reset_gpio) {
> > > /* Toggle ulpi to reset the phy. */
> > Does the comment above still apply?
> Now you mention it, the comment never made any sense anyway.
>
Then can we remove it?
>
> > > - gpiod_set_value_cansleep(reset_gpio, 1);
> > > usleep_range(5000, 10000);
> > Do we still need this usleep_range here?
>
> Yes, this is the "reset active" time.
>
But why do we need 2 calls to usleep_range? From just looking at this
here, it appears that the first was intended for the removed
gpiod_set_value_cansleep(reset_gpio, 1). If this "reset active" time is
needed irrespective of the existent reset_gpio, then shouldn't it be set
outside of this if statement?
BR,
Thinh
>
>
> >
> > BR,
> > Thinh
> >
> > > gpiod_set_value_cansleep(reset_gpio, 0);
> > > usleep_range(5000, 10000);
> > > --
> > > 2.43.0
> > >
> > >
> > > Met vriendelijke groet / kind regards,
> > >
> > > Mike Looijmans
> > >
> > >
>
> --
> Mike Looijmans
> System Expert
>
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