On Wed, Aug 28, 2024, Prashanth K wrote:

When operating in High-Speed, it is observed that DSTS[USBLNKST] doesn't update link state immediately after receiving the wakeup interrupt. Since wakeup event handler calls the resume callbacks, there is a chance that function drivers can perform an ep queue, which in turn tries to perform remote wakeup from send_gadget_ep_cmd(STARTXFER). This happens because DSTS[[21:18] wasn't updated to U0 yet, it's observed that the latency of DSTS can be in order of milli-seconds. Hence avoid calling gadget_wakeup during startxfer to prevent unnecessarily issuing remote wakeup to host.

Fixes: c36d8e947a56 ("usb: dwc3: gadget: put link to U0 before Start Transfer") Cc: stable@vger.kernel.org Suggested-by: Thinh Nguyen Thinh.Nguyen@synopsys.com Signed-off-by: Prashanth K quic_prashk@quicinc.com

---

v5: Further rewording of the comment in function. v4: Rewording the comment in function definition. v3: Added notes on top the function definition. v2: Refactored the patch as suggested in v1 discussion.

drivers/usb/dwc3/gadget.c | 41 ++++++++++++++++----------------------- 1 file changed, 17 insertions(+), 24 deletions(-)

diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c index 89fc690fdf34..291bc549935b 100644 --- a/drivers/usb/dwc3/gadget.c +++ b/drivers/usb/dwc3/gadget.c @@ -287,6 +287,23 @@ static int __dwc3_gadget_wakeup(struct dwc3 *dwc, bool async);

• Caller should handle locking. This function will issue @cmd with given
• @params to @dep and wait for its completion.

• • According to the programming guide, if the link state is in L1/L2/U3,
• • then sending the Start Transfer command may not complete. The
• • programming guide suggested to bring the link state back to ON/U0 by
• • performing remote wakeup prior to sending the command. However, don't
• • initiate remote wakeup when the user/function does not send wakeup
• • request via wakeup ops. Send the command when it's allowed.
• • Notes:
• • For L1 link state, issuing a command requires the clearing of
• • GUSB2PHYCFG.SUSPENDUSB2, which turns on the signal required to complete
• • the given command (usually within 50us). This should happen within the
• • command timeout set by driver. No additional step is needed.
• • For L2 or U3 link state, the gadget is in USB suspend. Care should be
• • taken when sending Start Transfer command to ensure that it's done after
• • USB resume.
  */

int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned int cmd, struct dwc3_gadget_ep_cmd_params *params) @@ -327,30 +344,6 @@ int dwc3_send_gadget_ep_cmd(struct dwc3_ep *dep, unsigned int cmd, dwc3_writel(dwc->regs, DWC3_GUSB2PHYCFG(0), reg); }

• if (DWC3_DEPCMD_CMD(cmd) == DWC3_DEPCMD_STARTTRANSFER) {

• int link_state;
  

• /*
  

•  * Initiate remote wakeup if the link state is in U3 when
  

•  * operating in SS/SSP or L1/L2 when operating in HS/FS. If the
  

•  * link state is in U1/U2, no remote wakeup is needed. The Start
  

•  * Transfer command will initiate the link recovery.
  

•  */
  

• link_state = dwc3_gadget_get_link_state(dwc);
  

• switch (link_state) {
  

• case DWC3_LINK_STATE_U2:
  

• 	if (dwc->gadget->speed >= USB_SPEED_SUPER)
  

• 		break;
  

• 	fallthrough;
  

• case DWC3_LINK_STATE_U3:
  

• 	ret = __dwc3_gadget_wakeup(dwc, false);
  

• 	dev_WARN_ONCE(dwc->dev, ret, "wakeup failed --> %d\n",
  

• 			ret);
  

• 	break;
  

• }
  

• }
• /*
  • For some commands such as Update Transfer command, DEPCMDPARn
  • registers are reserved. Since the driver often sends Update Transfer

-- 2.25.1

Acked-by: Thinh Nguyen Thinh.Nguyen@synopsys.com

Thanks, Thinh