Re: [RFC PATCH v2 1/3] usb: dwc3: Flush pending SETUP data during stop active xfers

Thinh Nguyen
2022-04-04T23:32:40Z

Wesley Cheng wrote:
>
>
> On 3/24/2022 6:51 PM, Thinh Nguyen wrote:
>> Wesley Cheng wrote:
>>> Hi Thinh,
>>>
>>> On 3/23/2022 5:39 PM, Thinh Nguyen wrote:
>>>> Hi Wesley,
>>>>
>>>> Wesley Cheng wrote:
>>>>> Hi Thinh,
>>>>>
>>>>> On 3/22/2022 6:31 PM, Thinh Nguyen wrote:
>>>>>> Hi Wesley,
>>>>>>
>>>>>> Wesley Cheng wrote:
>>>>>>> Hi Thinh,
>>>>>>>
>>>>>>> On 2/15/2022 4:08 PM, Wesley Cheng wrote:
>>>>>>>> While running the pullup disable sequence, if there are pending SETUP
>>>>>>>> transfers stored in the controller, then the ENDTRANSFER commands on non
>>>>>>>> control eps will fail w/ ETIMEDOUT. As a suggestion from SNPS, in order
>>>>>>>> to drain potentially cached SETUP packets, SW needs to issue a
>>>>>>>> STARTTRANSFER command. After issuing the STARTTRANSFER, and retrying the
>>>>>>>> ENDTRANSFER, the command should succeed. Else, if the endpoints are not
>>>>>>>> properly stopped, the controller halt sequence will fail as well.
>>>>>>>>
>>>>>>>> One limitation is that the current logic will drop the SETUP data
>>>>>>>> being received (ie dropping the SETUP packet), however, it should be
>>>>>>>> acceptable in the pullup disable case, as the device is eventually
>>>>>>>> going to disconnect from the host.
>>>>>>>>
>>>>>>>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
>>>>>>>> ---
>>>>>>> Just wondering if you had any inputs for this particular change? I
>>>>>>> think on the dequeue path discussion you had some concerns with parts of
>>>>>>> this change? I think the difficult part for the pullup disable path is
>>>>>>> that we have this API running w/ interrupts disabled, so the EP0 state
>>>>>>> won't be able to advance compared to the dequeue case.
>>>>>>
>>>>>> This doesn't sound right. The pullup disable (or device initiated
>>>>>> disconnect) should wait for the EP0 state to be EP0_SETUP_PHASE before
>>>>>> proceeding, which it does.
>>>>>>
>>>>> That is correct, but even though that check is passed, it doesn't
>>>>> prevent the host from sending another SETUP token between the pending
>>>>> setup packet check and run/stop clear.
>>>>>
>>>>
>>>> That should be fine, because we would have the TRB ready for that SETUP
>>>> packet.
>>>>
>>> I agree, its valid for the controller to be able to receive the next
>>> setup packet.
>>>
>>>>>>>
>>>>>>> Ideally, if there is a way to ensure that we avoid reading further setup
>>>>>>> packets, that would be nice, but from our discussions with Synopsys,
>>>>>>> this was not possible. (controller is always armed and ready to ACK
>>>>>>> setup tokens)
>>>>>>>
>>>>>>> I did evaluate keeping IRQs enabled and periodically releasing/attaining
>>>>>>> the lock between the stop active xfer calls, but that opened another can
>>>>>>> of worms. If you think this is the approach we should take, I can take
>>>>>>> a look at this implementation further.
>>>>>>>
>>>>>>
>>>>>> This patch doesn't look right to me. The change I suggested before
>>>>>> should address this (I believe Greg already picked it up). What other
>>>>>> problem do you see, I'm not clear what's the problem here. One potential
>>>>>> problem that I can see is that currently dwc3 driver doesn't wait for
>>>>>> active endpoints to complete/end before clearing the run_stop bit on
>>>>>> device initiated disconnect, but I'm not sure if that's what you're seeing.
>>>>>>
>>>>>> Please help clarify further. If there's trace points log, that'd help.
>>>>>>
>>>>> Main difference between the issue Greg recently pulled in and this one
>>>>> is that this is on the pullup disable patch (no dequeue involved). In
>>>>> this situation we will also stop active transfers, so that the
>>>>> controller can halt properly.
>>>>>
>>>>> I attached a few files, and will give a summary of them below:
>>>>> 1. pullup_disable_timeout.txt - ftrace of an instance of when we see
>>>>> several endxfer timeouts. Refer to line#2016.
>>>>>
>>>>> 2. lecroy+ftrace_snip.png - picture showing a matching bus sniffer log
>>>>> and a ftrace collected (difference instance to #1)
>>>>>
>>>>> #2 will show that we completed a SETUP transfer before entering into
>>>>> dwc3_gadget_stop_active_transfers(). In here, we then see DWC ACK
>>>>> another SETUP token, which leads to endxfer timeouts on all subsequent
>>>>> endpoints.
>>>>
>>>> Thanks for the captures. I think the problem here is because the dwc3
>>>> driver disables the control endpoint. It shouldn't do that.
>>>>
>>>> Can you try this:
>>>>
>>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>>> index ab725d2262d6..f0b9ea353620 100644
>>>> --- a/drivers/usb/dwc3/gadget.c
>>>> +++ b/drivers/usb/dwc3/gadget.c
>>>> @@ -1010,12 +1010,12 @@ static int __dwc3_gadget_ep_disable(struct
>>>> dwc3_ep *dep)
>>>> if (dep->flags & DWC3_EP_STALL)
>>>> __dwc3_gadget_ep_set_halt(dep, 0, false);
>>>>
>>>> - reg = dwc3_readl(dwc->regs, DWC3_DALEPENA);
>>>> - reg &= ~DWC3_DALEPENA_EP(dep->number);
>>>> - dwc3_writel(dwc->regs, DWC3_DALEPENA, reg);
>>>> -
>>>> - /* Clear out the ep descriptors for non-ep0 */
>>>> if (dep->number > 1) {
>>>> + reg = dwc3_readl(dwc->regs, DWC3_DALEPENA);
>>>> + reg &= ~DWC3_DALEPENA_EP(dep->number);
>>>> + dwc3_writel(dwc->regs, DWC3_DALEPENA, reg);
>>>> +
>>>> + /* Clear out the ep descriptors for non-ep0 */
>>>> dep->endpoint.comp_desc = NULL;
>>>> dep->endpoint.desc = NULL;
>>>> }
>>>>
>>> I was able to reproduce the endxfer timeout w/ the above change. I'm
>>> assuming you didn't want me to include any parts of my change while
>>> testing, right?
>>>
>>
>> Right, please don't add additional code. I can't review knowing what
>> else was changed.
>>
>>> Current sequence in dwc3_gadget_pullup(0) is that we should call
>>> dwc3_stop_active_transfers() before we call __dwc3_gadget_stop().
>>> (gadget stop will call the ep disable for EP[0] and EP[1]) This might
>>> be why the issue would still be occurring.
>>>
>>> The attached ftrace that captures a situation where a forced BUG will
>>> occur on the first instance of the timeout.
>>>
>>> [ 1573.687689437 0x724885c22] event (000020c0): ep0out: Transfer
>>> Not Ready [0] (Not Active) [Status Phase]
>>> [ 1573.687738707 0x724885fd3] dbg_send_ep_cmd: ep0out: cmd
>>> 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status:
>>> Successful
>>> [ 1573.698040582 0x7248b6477] dbg_send_ep_cmd: ep1out: cmd 'End
>>> Transfer' [20c08] params 00000000 00000000 00000000 --> status: Timed Out
>>>
>>> We definitely started the STATUS phase, so host could have read it and
>>> sent the next SETUP packet while we were already in the
>>> dwc3_stop_active_transfers() loop.
>>
>> Yeah, pullup() is another async call that can trigger the same problem.
>>
>>
>>
>> [ 1573.687193134 0x7248836e8] dbg_send_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: Successful
>> [ 1573.687263291 0x724883c2b] event (0000c040): ep0out: Transfer Complete (sIL) [Setup Phase]
>> [ 1573.687287145 0x724883df6] dbg_trace_log_ctrl: Clear Interface Feature(Function Suspend)
>>
>> Trace indicates that this is ClearFeature(Interface.FuncSuspend)
>>
>>
>> [ 1573.687372301 0x724884459] dbg_send_ep_cmd: ep0in: cmd 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: Successful
>> [ 1573.687400634 0x724884679] event (000010c2): ep0in: Transfer Not Ready [0] (Not Active) [Data Phase]
>> [ 1573.687471155 0x724884bc2] event (000090c2): ep0in: Transfer Not Ready [0] (Active) [Data Phase]
>> [ 1573.687495009 0x724884d8d] event (0000c042): ep0in: Transfer Complete (sIL) [Data Phase]
>> [ 1573.687544697 0x724885146] dbg_gadget_giveback: ep0out: req ffffff87a6768800 length 20/20 ZsI ==> 0
>>
>> But there's data stage. Is this non-standard/vendor request?
>> We probably need to fix the tracepoint to properly print vendor
>> requests.
>>
>>
>> [ 1573.687593187 0x7248854e9] dbg_ep_queue: ep5in: req ffffff87a6769000 length 0/8 zsI ==> -115
>> [ 1573.687619645 0x7248856e6] dbg_prepare: ep5in: trb ffffffc05a97d1a0 (E27:D26) buf 00000000ee07f600 size 1x 8 ctrl 00000811 (Hlcs:sC:normal)
>> [ 1573.687660270 0x7248859f2] dbg_send_ep_cmd: ep5in: cmd 'Update Transfer' [b0007] params 00000000 00000000 00000000 --> status: Successful
>> [ 1573.687689437 0x724885c22] event (000020c0): ep0out: Transfer Not Ready [0] (Not Active) [Status Phase]
>> [ 1573.687738707 0x724885fd3] dbg_send_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: Successful
>>
>> It's still in status stage, it never reached Setup phase.
>>
>>
>> [ 1573.698040582 0x7248b6477] dbg_send_ep_cmd: ep1out: cmd 'End Transfer' [20c08] params 00000000 00000000 00000000 --> status: Timed Out
>>
>> That's why it's possible to time out here. The Setup Phase should
>> have been prepared before we can issue End Transfer.
>>
>> I can't see where the pullup() begins as this log is missing register
>> read/write trace events. Looks like the wait_for_completion_timeout()
>> is insufficient. I assume it happens right after previous Setup
>> phase. There's no spin_lock, so the driver can proceed with the
>> new control request before it reaches dwc3_stop_active_transfers().
>>
>> Can you try this. (yes, the code looks ugly right now, but it's just
>> to confirm my suspicion)
>>
>
> Hi Thinh,
>
> So I tried a few things, and will highlight the results below.
>
> #1 Changes recommended below:
> - Ran into a situation where there was still a potential SETUP packet
> being received while looping through the available EPs.
> - Attached the log to this email. Please refer to the notations near
> the end of the trace (testchanges_trace.txt):
>
> //Last SETUP transaction before dwc3_gadget_stop_active_transfers()
> //dwc3_gadet_stop_active_transfers() loop starting below w/ ep1out
> [ 15144.915547414 0x43cfbf36a2] dbg_send_ep_cmd: ep1out: cmd
> 'End Transfer' [20c08] params 00000000 00000000 00000000 --> status:
> Successful
> [ 15144.915585487 0x43cfbf397c] dbg_gadget_giveback: ep1out: req
> ffffff87a5f89700 length 0/16384 zsI ==> -108
> [ 15144.915619966 0x43cfbf3c13] event (0000c040): ep0out:
> Transfer Complete (sIL) [Setup Phase]
> [ 15144.915662153 0x43cfbf3f3d] dbg_trace_log_ctrl: Get String
> Descriptor(Index = 9, Length = 510)
> ...
>

> //Finished 'Get String Descriptor" packet, and able to receive next SETUP

No, it's not finished here and the SETUP is not prepared yet.

[ 15144.916351580 0x43cfbf72f2] event (000020c0): ep0out: Transfer Not Ready [0] (Not Active) [Status Phase]
[ 15144.916419185 0x43cfbf7803] dbg_send_ep_cmd: ep0out: cmd 'Start Transfer' [406] params 00000000 efffa000 00000000 --> status: Successful

dwc3 just started the Status stage. It did not prepare for the next SETUP
phase yet.

> ...
> Transfer' [f0c08] params 00000000 00000000 00000000 --> status: Timed Out

That's why it's timed out.

>
>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>> index ab725d2262d6..3b40411556ff 100644
>> --- a/drivers/usb/dwc3/gadget.c
>> +++ b/drivers/usb/dwc3/gadget.c
>> @@ -2506,6 +2506,8 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>>
>> is_on = !!is_on;
>> dwc->softconnect = is_on;
>> +
>> +retry:
>> /*
>> * Per databook, when we want to stop the gadget, if a control transfer
>> * is still in process, complete it and get the core into setup phase.
>> @@ -2541,6 +2543,24 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>> return 0;
>> }
>>
>> + if (!is_on) {
>> + spin_lock_irqsave(&dwc->lock, flags);
>> + if (dwc->ep0state != EP0_SETUP_PHASE) {
>> + spin_unlock_irqrestore(&dwc->lock, flags);
>> + goto retry;
>> + }
>> +
>> + /*
>> + * In the Synopsis DesignWare Cores USB3 Databook Rev. 3.30a
>> + * Section 4.1.8 Table 4-7, it states that for a device-initiated
>> + * disconnect, the SW needs to ensure that it sends "a DEPENDXFER
>> + * command for any active transfers" before clearing the RunStop
>> + * bit.
>> + */
>> + dwc3_stop_active_transfers(dwc);

The reason why my suggestion test patch didn't work is because
dwc3_stop_active_transfers() also "gives back" requests in its loop. When
the driver gives back requests, it does spin_unlock() allowing the
driver to service the next request. I was hoping that the driver will
block servicing new control requests until dwc3_stop_active_transfers()
completes.

>> + spin_unlock_irqrestore(&dwc->lock, flags);
>> + }
>> +
>> /*
>> * Synchronize and disable any further event handling while controller
>> * is being enabled/disabled.
>> @@ -2553,14 +2573,6 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>> u32 count;
>>
>> dwc->connected = false;
>> - /*
>> - * In the Synopsis DesignWare Cores USB3 Databook Rev. 3.30a
>> - * Section 4.1.8 Table 4-7, it states that for a device-initiated
>> - * disconnect, the SW needs to ensure that it sends "a DEPENDXFER
>> - * command for any active transfers" before clearing the RunStop
>> - * bit.
>> - */
>> - dwc3_stop_active_transfers(dwc);
>> __dwc3_gadget_stop(dwc);
>>
>> /*
>>
>
> #2 I built on top of the changes you suggested, and added the ep0state
> check within dwc3_stop_active_transfers(). Utilized the
> DWC3_EP_DELAY_STOP (flag from the dequeue endxfer patch) to have the ep0
> driver issue the endxfer. With the changes below, I haven't seen the
> failure so far. Anyway, this is just the initial version of the changes
> I've made, but I think its a cleaner approach than the changes that were
> submitted in the RFC.
>
> Also, with releasing the lock here, I had to add the changes we had
> previously proposed here as well to prevent a list corruption:
>
> https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/1620716636-12422-1-git-send-email-wcheng@codeaurora.org/__;!!A4F2R9G_pg!OrdWZ7WUdndzskqgSWKiIV9RRJTgw1rptjjxGBhEeb_VRVNTCkmIQs29ls-DGqjp3OJa$
>
> https://urldefense.com/v3/__https://lore.kernel.org/linux-usb/89bb9ef4-f85e-5ccf-9288-780efec72f5c@synopsys.com/__;!!A4F2R9G_pg!OrdWZ7WUdndzskqgSWKiIV9RRJTgw1rptjjxGBhEeb_VRVNTCkmIQs29ls-DGr-w0Z-S$
>
>
> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
> index 1064be5518f6..aba3491eadf9 100644
> --- a/drivers/usb/dwc3/ep0.c
> +++ b/drivers/usb/dwc3/ep0.c
> @@ -273,8 +273,6 @@ void dwc3_ep0_out_start(struct dwc3 *dwc)
> int ret;
> int i;
>
> - complete(&dwc->ep0_in_setup);
> -
> dep = dwc->eps[0];
> dwc3_ep0_prepare_one_trb(dep, dwc->ep0_trb_addr, 8,
> DWC3_TRBCTL_CONTROL_SETUP, false);
> @@ -291,8 +289,10 @@ void dwc3_ep0_out_start(struct dwc3 *dwc)
> continue;
>
> dwc3_ep->flags &= ~DWC3_EP_DELAY_STOP;
> - dwc3_stop_active_transfer(dwc3_ep, true, true);
> + dwc3_stop_active_transfer(dwc3_ep, true, dwc->softconnect ?
> + true : false);

Do you mean to do this?

dwc3_stop_active_transfer(dwc3_ep, true, !dwc->softconnect)

> }
> + complete(&dwc->ep0_in_setup);
> }
>
> static struct dwc3_ep *dwc3_wIndex_to_dep(struct dwc3 *dwc, __le16
> wIndex_le)
> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
> index b0b225b157b4..86f81e5f66ba 100644
> --- a/drivers/usb/dwc3/gadget.c
> +++ b/drivers/usb/dwc3/gadget.c
> @@ -882,12 +882,13 @@ static int __dwc3_gadget_ep_enable(struct dwc3_ep
> *dep, unsigned int action)
> reg |= DWC3_DALEPENA_EP(dep->number);
> dwc3_writel(dwc->regs, DWC3_DALEPENA, reg);
>
> - if (usb_endpoint_xfer_control(desc))
> - goto out;
> -
> /* Initialize the TRB ring */
> dep->trb_dequeue = 0;
> dep->trb_enqueue = 0;
> +
> + if (usb_endpoint_xfer_control(desc))
> + goto out;
> +
> memset(dep->trb_pool, 0,
> sizeof(struct dwc3_trb) * DWC3_TRB_NUM);
>
> @@ -1889,7 +1890,8 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep
> *dep, struct dwc3_request *req)
> {
> struct dwc3 *dwc = dep->dwc;
>
> - if (!dep->endpoint.desc || !dwc->pullups_connected || !dwc->connected) {
> + if (!dep->endpoint.desc || !dwc->pullups_connected || !dwc->connected ||
> + !dwc->softconnect) {
> dev_dbg(dwc->dev, "%s: can't queue to disabled endpoint\n",
> dep->name);
> return -ESHUTDOWN;
> @@ -2348,6 +2350,7 @@ static int dwc3_gadget_set_selfpowered(struct
> usb_gadget *g,
>
> static void dwc3_stop_active_transfers(struct dwc3 *dwc)
> {
> + int ret;
> u32 epnum;
>
> for (epnum = 2; epnum < dwc->num_eps; epnum++) {
> @@ -2357,6 +2360,19 @@ static void dwc3_stop_active_transfers(struct
> dwc3 *dwc)
> if (!dep)
> continue;
>
> + if (dwc->ep0state != EP0_SETUP_PHASE) {
> + dep->flags |= DWC3_EP_DELAY_STOP;
> + spin_unlock(&dwc->lock);
> +
> + reinit_completion(&dwc->ep0_in_setup);
> +
> + ret = wait_for_completion_timeout(&dwc->ep0_in_setup,
> + msecs_to_jiffies(DWC3_PULL_UP_TIMEOUT));
> + if (ret == 0)
> + dev_warn(dwc->dev, "timed out waiting for SETUP phase\n");
> + spin_lock(&dwc->lock);
> + }
> +

This alleviates the problem, but doesn't completely prevent it.

> dwc3_remove_requests(dwc, dep);
> }
> }
> @@ -2547,6 +2563,19 @@ static int dwc3_gadget_pullup(struct usb_gadget
> *g, int is_on)
> return 0;
> }
>
> + if (!is_on) {
> + spin_lock_irqsave(&dwc->lock, flags);
> + /*
> + * In the Synopsis DesignWare Cores USB3 Databook Rev. 3.30a
> + * Section 4.1.8 Table 4-7, it states that for a device-initiated
> + * disconnect, the SW needs to ensure that it sends "a DEPENDXFER
> + * command for any active transfers" before clearing the RunStop
> + * bit.
> + */
> + dwc3_stop_active_transfers(dwc);
> + spin_unlock_irqrestore(&dwc->lock, flags);
> + }
> +
> /*
> * Synchronize and disable any further event handling while controller
> * is being enabled/disabled.
> @@ -2559,14 +2588,6 @@ static int dwc3_gadget_pullup(struct usb_gadget
> *g, int is_on)
> u32 count;
>
> dwc->connected = false;
> - /*
> - * In the Synopsis DesignWare Cores USB3 Databook Rev. 3.30a
> - * Section 4.1.8 Table 4-7, it states that for a device-initiated
> - * disconnect, the SW needs to ensure that it sends "a DEPENDXFER
> - * command for any active transfers" before clearing the RunStop
> - * bit.
> - */
> - dwc3_stop_active_transfers(dwc);

This will still run into the same problem.

> __dwc3_gadget_stop(dwc);
>
> /*
> @@ -3334,7 +3355,7 @@ static bool dwc3_gadget_ep_should_continue(struct
> dwc3_ep *dep)
> struct dwc3 *dwc = dep->dwc;
>
> if (!dep->endpoint.desc || !dwc->pullups_connected ||
> - !dwc->connected)
> + !dwc->connected || !dwc->softconnect)
> return false;
>
> if (!list_empty(&dep->pending_list))
>

Looking at the pullup() function again, it needs some rework on top
of the problem we already have here. I'll try to rewrite it later this
week or the next. If you new updates, I'll be happy to review it.

Thanks,
Thinh