Commit 00dcf2fa authored by Prashanth K's avatar Prashanth K Committed by Greg Kroah-Hartman
Browse files

usb: dwc3: Avoid waking up gadget during startxfer 



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: c36d8e94 ("usb: dwc3: gadget: put link to U0 before Start Transfer")
Cc: stable@vger.kernel.org
Suggested-by: default avatarThinh Nguyen <Thinh.Nguyen@synopsys.com>
Signed-off-by: default avatarPrashanth K <quic_prashk@quicinc.com>
Acked-by: default avatarThinh Nguyen <Thinh.Nguyen@synopsys.com>
Link: https://lore.kernel.org/r/20240828064302.3796315-1-quic_prashk@quicinc.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 431c1646

drivers/usb/dwc3/gadget.c

+17 −24
Original line number Diff line number Diff line
@@ -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