[PATCH] usb: dwc3: fix abort on invalid ref clock rate from clk_get_rate()

[Peter Robinson]

Hi Frank,

There's a big rebase to sync with upstream Linux driver [1][2], I
think it's due to land shortly, does the issue still occur with that?

It would be good to get the rockchips SoCs with the dwc3 controller
tested with that rebase.

Peter

[1] https://lists.u-boot-project.org/pipermail/u-boot/2026-October/637669.html
[2] https://lists.u-boot-project.org/pipermail/u-boot/2026-October/637734.html

On Tue, 3 Nov 2026 at 08:28, Frank Wang <frank.wang at rock-chips.com> wrote:
>
> On 32-bit platforms, "usb start" aborted with
> "### ERROR ### Please RESET the board ###". If the clock driver
> does not implement the "ref" clock, clk_get_rate() returns
> -ENOENT, which dwc3_ref_clk_period() treated as a valid rate.
> period became 0 and the fladj calculation divided by zero; the
> software 64-bit division on 32-bit ARM calls the
> division-by-zero handler __div0() and hangs (64-bit platforms
> survive silently since UDIV returns 0).
>
> Skip REFCLKPER/GFLADJ programming when clk_get_rate() returns an
> error code, as is already done for rate == 0.
>
> Fixes: 6bae0eb5b8bd ("usb: dwc3: Calculate REFCLKPER based on reference clock")
> Signed-off-by: Frank Wang <frank.wang at rock-chips.com>
> ---
>  drivers/usb/dwc3/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
> index be198041f08..9a84ec6a60e 100644
> --- a/drivers/usb/dwc3/core.c
> +++ b/drivers/usb/dwc3/core.c
> @@ -151,7 +151,7 @@ static void dwc3_ref_clk_period(struct dwc3 *dwc)
>
>         if (dwc->ref_clk) {
>                 rate = clk_get_rate(dwc->ref_clk);
> -               if (!rate)
> +               if (!rate || IS_ERR_VALUE(rate))
>                         return;
>                 period = NSEC_PER_SEC / rate;
>         } else {
> --
> 2.17.1
>