| Message ID | 20240828064302.3796315-1-quic_prashk@quicinc.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 00dcf2fa449f23a263343d7fe051741bdde65d0b |
| Headers | show |
| Series | [v5] usb: dwc3: Avoid waking up gadget during startxfer | expand |
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
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
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(-)