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Date: Tue, 1 Sep 2020 18:50:28 -0700
From: Wesley Cheng <wcheng@...eaurora.org>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
"balbi@...nel.org" <balbi@...nel.org>,
"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
"jackp@...eaurora.org" <jackp@...eaurora.org>
Subject: Re: [PATCH v2] usb: dwc3: Stop active transfers before halting the
controller
On 9/1/2020 3:14 PM, Wesley Cheng wrote:
>
>
> On 8/29/2020 2:35 PM, Thinh Nguyen wrote:
>> Wesley Cheng wrote:
>>> In the DWC3 databook, for a device initiated disconnect or bus reset, the
>>> driver is required to send dependxfer commands for any pending transfers.
>>> In addition, before the controller can move to the halted state, the SW
>>> needs to acknowledge any pending events. If the controller is not halted
>>> properly, there is a chance the controller will continue accessing stale or
>>> freed TRBs and buffers.
>>>
>>> Signed-off-by: Wesley Cheng <wcheng@...eaurora.org>
>>>
>>> ---
>>> Changes in v2:
>>> - Moved cleanup code to the pullup() API to differentiate between device
>>> disconnect and hibernation.
>>> - Added cleanup code to the bus reset case as well.
>>> - Verified the move to pullup() did not reproduce the problen using the
>>> same test sequence.
>>>
>>> Verified fix by adding a check for ETIMEDOUT during the run stop call.
>>> Shell script writing to the configfs UDC file to trigger disconnect and
>>> connect. Batch script to have PC execute data transfers over adb (ie adb
>>> push) After a few iterations, we'd run into a scenario where the
>>> controller wasn't halted. With the following change, no failed halts after
>>> many iterations.
>>> ---
>>> drivers/usb/dwc3/ep0.c | 2 +-
>>> drivers/usb/dwc3/gadget.c | 52 ++++++++++++++++++++++++++++++++++++++-
>>> 2 files changed, 52 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/usb/dwc3/ep0.c b/drivers/usb/dwc3/ep0.c
>>> index 59f2e8c31bd1..456aa87e8778 100644
>>> --- a/drivers/usb/dwc3/ep0.c
>>> +++ b/drivers/usb/dwc3/ep0.c
>>> @@ -197,7 +197,7 @@ int dwc3_gadget_ep0_queue(struct usb_ep *ep, struct usb_request *request,
>>> int ret;
>>>
>>> spin_lock_irqsave(&dwc->lock, flags);
>>> - if (!dep->endpoint.desc) {
>>> + if (!dep->endpoint.desc || !dwc->pullups_connected) {
>>> dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
>>> dep->name);
>>> ret = -ESHUTDOWN;
>>> diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
>>> index 3ab6f118c508..df8d89d6bdc9 100644
>>> --- a/drivers/usb/dwc3/gadget.c
>>> +++ b/drivers/usb/dwc3/gadget.c
>>> @@ -1516,7 +1516,7 @@ static int __dwc3_gadget_ep_queue(struct dwc3_ep *dep, struct dwc3_request *req)
>>> {
>>> struct dwc3 *dwc = dep->dwc;
>>>
>>> - if (!dep->endpoint.desc) {
>>> + if (!dep->endpoint.desc || !dwc->pullups_connected) {
>>> dev_err(dwc->dev, "%s: can't queue to disabled endpoint\n",
>>> dep->name);
>>> return -ESHUTDOWN;
>>> @@ -1926,6 +1926,24 @@ static int dwc3_gadget_set_selfpowered(struct usb_gadget *g,
>>> return 0;
>>> }
>>>
>>> +static void dwc3_stop_active_transfers(struct dwc3 *dwc)
>>> +{
>>> + u32 epnum;
>>> +
>>> + for (epnum = 2; epnum < DWC3_ENDPOINTS_NUM; epnum++) {
>>> + struct dwc3_ep *dep;
>>> +
>>> + dep = dwc->eps[epnum];
>>> + if (!dep)
>>> + continue;
>>> +
>>> + if (!(dep->flags & DWC3_EP_ENABLED))
>>> + continue;
>>
>> Don't do the enabled check here. Let the dwc3_stop_active_transfer() do
>> that checking.
>>
>
> Hi Thinh,
>
> Thanks for the detailed review, as always. Got it, we can allow that to
> catch it based off the DWC3_EP_TRANSFER_STARTED.
>
>>> +
>>> + dwc3_remove_requests(dwc, dep);
>>> + }
>>> +}
>>> +
>>> static int dwc3_gadget_run_stop(struct dwc3 *dwc, int is_on, int suspend)
>>> {
>>> u32 reg;
>>> @@ -1994,9 +2012,39 @@ static int dwc3_gadget_pullup(struct usb_gadget *g, int is_on)
>>> }
>>> }
>>>
>>> + /*
>>> + * Synchronize and disable any further event handling while controller
>>> + * is being enabled/disabled.
>>> + */
>>> + disable_irq(dwc->irq_gadget);
>>
>> I think it's better to do dwc3_gadget_disable_irq(). This only stops
>> handling events. Although it's unlikely, the controller may still
>> generate events before it's halted.
>>
>
> I think its better if we can do both. At least with the disable_irq()
> call present, we can ensure the irq handlers are complete, or we can do
> as Felipe suggested, and first disable the controller events (using
> dwc3_gadget_disable_irq()) and then calling synchronize_irq().
>
> The concern I had is the pullup() API updating the lpos, and the hardirq
> handler referencing it to update the evt buf cache and waking up the
> threaded irq handler. (since we don't clear the evt->count explicitly,
> it may reference empty/stale events)
>
>>> spin_lock_irqsave(&dwc->lock, flags);
>>> +
>>> + /* Controller is not halted until pending events are acknowledged */
>>> + if (!is_on) {
>>> + u32 reg;
>>> +
>>> + __dwc3_gadget_ep_disable(dwc->eps[0]);
>>> + __dwc3_gadget_ep_disable(dwc->eps[1]);
>>
>> You can just do __dwc3_gadget_stop(), and do that after
>> dwc3_stop_active_transfers().
>>
>
> Got it.
>
Hi Thinh,
Maybe we can ignore calling dwc3_gadget_disable_irq() separately if we
are going to use __dwc3_gadget_stop(), since gadget stop will call
dwc3_gadget_disable_irq(). Also, it would be executed before the event
count clearing, so if there was an event (unlikely) that was generated,
we would discard it.
Something like:
disable_irq(dwc->irq_gadget);
spin_lock_irqsave(&dwc->lock, flags);
if (!is_on) {
u32 count;
dwc3_stop_active_transfers(dwc);
__dwc3_gadget_stop(dwc);
count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
count &= DWC3_GEVNTCOUNT_MASK;
Thanks
Wesley
>>> +
>>> + /*
>>> + * The databook explicitly mentions for a device-initiated
>>> + * disconnect sequence, the SW needs to ensure that it ends any
>>> + * active transfers.
>>> + */
>>> + dwc3_stop_active_transfers(dwc);
>>> +
>>> + reg = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
>>> + reg &= DWC3_GEVNTCOUNT_MASK;
>>
>> Can we use another variable "count" instead of reusing reg to make it a
>> little clearer?
>>
>
> Sure, I'll add another variable.
>
> Thanks
> Wesley
>
>>> + if (reg > 0) {
>>> + dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), reg);
>>> + dwc->ev_buf->lpos = (dwc->ev_buf->lpos + reg) %
>>> + dwc->ev_buf->length;
>>> + }
>>> + }
>>> +
>>> ret = dwc3_gadget_run_stop(dwc, is_on, false);
>>> spin_unlock_irqrestore(&dwc->lock, flags);
>>> + enable_irq(dwc->irq_gadget);
>>>
>>> return ret;
>>> }
>>> @@ -3100,6 +3148,8 @@ static void dwc3_gadget_reset_interrupt(struct dwc3 *dwc)
>>> }
>>>
>>> dwc3_reset_gadget(dwc);
>>> + /* Stop any active/pending transfers when receiving bus reset */
>>> + dwc3_stop_active_transfers(dwc);
>>>
>>> reg = dwc3_readl(dwc->regs, DWC3_DCTL);
>>> reg &= ~DWC3_DCTL_TSTCTRL_MASK;
>>
>> Looks good to me.
>>
>> Thanks,
>> Thinh
>>
>
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