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