Re: [PATCH] usb: dwc3: xilinx: Prevent spike in reset signal
From: Thinh Nguyen
Date: Fri Mar 14 2025 - 17:15:03 EST
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?
>
> 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?
> - gpiod_set_value_cansleep(reset_gpio, 1);
> usleep_range(5000, 10000);
Do we still need this usleep_range here?
BR,
Thinh
> gpiod_set_value_cansleep(reset_gpio, 0);
> usleep_range(5000, 10000);
> --
> 2.43.0
>
>
> Met vriendelijke groet / kind regards,
>
> Mike Looijmans
> System Expert
>
>
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