On Sat, Feb 01, 2025, Selvarasu Ganesan wrote:
> There is a frequent timeout during controller enter/exit from halt state
> after toggling the run_stop bit by SW. This timeout occurs when
> performing frequent role switches between host and device, causing
> device enumeration issues due to the timeout. This issue was not present
> when USB2 suspend PHY was disabled by passing the SNPS quirks
> (snps,dis_u2_susphy_quirk and snps,dis_enblslpm_quirk) from the DTS.
> However, there is a requirement to enable USB2 suspend PHY by setting of
> GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY bits when controller starts
> in gadget or host mode results in the timeout issue.
>
> This commit addresses this timeout issue by ensuring that the bits
> GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY are cleared before starting
> the dwc3_gadget_run_stop sequence and restoring them after the
> dwc3_gadget_run_stop sequence is completed.
>
> Fixes: 72246da40f37 ("usb: Introduce DesignWare USB3 DRD Driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Selvarasu Ganesan <selvarasu.g@xxxxxxxxxxx>
> ---
>
> Changes in v2:
> - Added some comments before the changes.
> - And removed "unlikely" in the condition check.
> - Link to v1: https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/20250131110832.438-1-selvarasu.g@xxxxxxxxxxx/__;!!A4F2R9G_pg!aIY9c56j1jjbSvIIW4zaudkdAGozvtMu-PwjhrMy0_v0FxGBaYhMXS8fTrVTzEOevr8QitekXvuOPKPfDxiHGa93hjI$
> ---
> drivers/usb/dwc3/gadget.c | 34 ++++++++++++++++++++++++++++++++++
> 1 file changed, 34 insertions(+)
>
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index d27af65eb08a..ddd6b2ce5710 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -2629,10 +2629,38 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on)
> {
> u32 reg;
> u32 timeout = 2000;
> + u32 saved_config = 0;
>
> if (pm_runtime_suspended(dwc->dev))
> return 0;
>
> + /*
> + * When operating in USB 2.0 speeds (HS/FS), ensure that
> + * GUSB2PHYCFG.ENBLSLPM and GUSB2PHYCFG.SUSPHY are cleared before starting
> + * or stopping the controller. This resolves timeout issues that occur
> + * during frequent role switches between host and device modes.
> + *
> + * Save and clear these settings, then restore them after completing the
> + * controller start or stop sequence.
> + *
> + * This solution was discovered through experimentation as it is not
> + * mentioned in the dwc3 programming guide. It has been tested on an
> + * Exynos platforms.
> + */
> + reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
> + if (reg & DWC3_GUSB2PHYCFG_SUSPHY) {
> + saved_config |= DWC3_GUSB2PHYCFG_SUSPHY;
> + reg &= ~DWC3_GUSB2PHYCFG_SUSPHY;
> + }
> +
> + if (reg & DWC3_GUSB2PHYCFG_ENBLSLPM) {
> + saved_config |= DWC3_GUSB2PHYCFG_ENBLSLPM;
> + reg &= ~DWC3_GUSB2PHYCFG_ENBLSLPM;
> + }
> +
> + if (saved_config)
> + dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
> +
> reg = dwc3_readl(dwc->regs, DWC3_DCTL);
> if (is_on) {
> if (DWC3_VER_IS_WITHIN(DWC3, ANY, 187A)) {
> @@ -2660,6 +2688,12 @@ static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on)
> reg &= DWC3_DSTS_DEVCTRLHLT;
> } while (--timeout && !(!is_on ^ !reg));
>
> + if (saved_config) {
> + reg = dwc3_readl(dwc->regs, DWC3_GUSB2PHYCFG(0));
> + reg |= saved_config;
> + dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg);
> + }
> +
> if (!timeout)
> return -ETIMEDOUT;
>
> --
> 2.17.1
>
Acked-by: Thinh Nguyen <Thinh.Nguyen@xxxxxxxxxxxx>
Thanks,
Thinh
