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    SubjectRe: [RFC] usb: dwc3: core: Fix RAM interface getting stuck during enumeration
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    On 10/13/2023 12:55 AM, Wesley Cheng wrote:
    > Hi Krishna,
    >
    > On 10/11/2023 3:02 AM, Krishna Kurapati wrote:
    >> This implementation is to fix RAM interface getting stuck during

    >> Synopsys confirmed that the issue is present on all USB3 devices and
    >> as a workaround, suggested to re-initialize device mode.
    >>
    >> Signed-off-by: Krishna Kurapati <quic_kriskura@quicinc.com>
    >> ---
    >>   drivers/usb/dwc3/core.c   | 20 ++++++++++++++++++++
    >>   drivers/usb/dwc3/core.h   |  4 ++++
    >>   drivers/usb/dwc3/drd.c    |  5 +++++
    >>   drivers/usb/dwc3/gadget.c |  6 ++++--
    >>   4 files changed, 33 insertions(+), 2 deletions(-)
    >>
    >> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
    >> index 44ee8526dc28..d18b81cccdc5 100644
    >> --- a/drivers/usb/dwc3/core.c
    >> +++ b/drivers/usb/dwc3/core.c
    >> @@ -122,6 +122,7 @@ static void __dwc3_set_mode(struct work_struct *work)
    >>       unsigned long flags;
    >>       int ret;
    >>       u32 reg;
    >> +    u8 timeout = 100;
    >>       u32 desired_dr_role;
    >>       mutex_lock(&dwc->mutex);
    >> @@ -137,6 +138,25 @@ static void __dwc3_set_mode(struct work_struct
    >> *work)
    >>       if (!desired_dr_role)
    >>           goto out;
    >> +    /*
    >> +     * STAR 5001544 - If cable disconnect doesn't generate
    >> +     * disconnect event in device mode, then re-initialize the
    >> +     * controller.
    >> +     */
    >> +    if ((dwc->cable_disconnected == true) &&
    >> +        (dwc->current_dr_role == DWC3_GCTL_PRTCAP_DEVICE)) {
    >> +        while (dwc->connected == true && timeout != 0) {
    >> +            mdelay(10);
    >> +            timeout--;
    >> +        }
    >> +
    >> +        if (timeout == 0) {
    >> +            dwc3_gadget_soft_disconnect(dwc);
    >> +            udelay(100);
    >> +            dwc3_gadget_soft_connect(dwc);
    >> +        }
    >> +    }
    >> +
    >>       if (desired_dr_role == dwc->current_dr_role)
    >>           goto out;
    >> diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
    >> index c6c87acbd376..7642330cf608 100644
    >> --- a/drivers/usb/dwc3/core.h
    >> +++ b/drivers/usb/dwc3/core.h
    >> @@ -1355,6 +1355,7 @@ struct dwc3 {
    >>       int            last_fifo_depth;
    >>       int            num_ep_resized;
    >>       struct dentry        *debug_root;
    >> +    bool            cable_disconnected;
    >>   };
    >>   #define INCRX_BURST_MODE 0
    >> @@ -1568,6 +1569,9 @@ void dwc3_event_buffers_cleanup(struct dwc3 *dwc);
    >>   int dwc3_core_soft_reset(struct dwc3 *dwc);
    >> +int dwc3_gadget_soft_disconnect(struct dwc3 *dwc);
    >> +int dwc3_gadget_soft_connect(struct dwc3 *dwc);
    >> +
    >>   #if IS_ENABLED(CONFIG_USB_DWC3_HOST) ||
    >> IS_ENABLED(CONFIG_USB_DWC3_DUAL_ROLE)
    >>   int dwc3_host_init(struct dwc3 *dwc);
    >>   void dwc3_host_exit(struct dwc3 *dwc);
    >> diff --git a/drivers/usb/dwc3/drd.c b/drivers/usb/dwc3/drd.c
    >> index 039bf241769a..593c023fc39a 100644
    >> --- a/drivers/usb/dwc3/drd.c
    >> +++ b/drivers/usb/dwc3/drd.c
    >> @@ -446,6 +446,8 @@ static int dwc3_usb_role_switch_set(struct
    >> usb_role_switch *sw,
    >>       struct dwc3 *dwc = usb_role_switch_get_drvdata(sw);
    >>       u32 mode;
    >> +    dwc->cable_disconnected = false;
    >> +
    >>       switch (role) {
    >>       case USB_ROLE_HOST:
    >>           mode = DWC3_GCTL_PRTCAP_HOST;
    >> @@ -454,6 +456,9 @@ static int dwc3_usb_role_switch_set(struct
    >> usb_role_switch *sw,
    >>           mode = DWC3_GCTL_PRTCAP_DEVICE;
    >>           break;
    >>       default:
    >> +        if (role == USB_ROLE_NONE)
    >> +            dwc->cable_disconnected = true;
    >> +
    >
    > How do we handle cases where role switch isn't used? (ie extcon or maybe
    > no cable connection notification at all)
    >

    Hi Wesley,

    Since I was considering fixing it during disconnect, I made it in role
    switch. So no cable connection notification case has been ruled out in
    this patch. But yes, extcon is a valid case. Will need to account for it.

    Regards,
    Krishna,

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