Re: [PATCH] usb: dwc3: Potential fix of possible dwc3 interrupt storm

[Selvarasu Ganesan <selvarasu.g@samsung.com>]

On 9/13/2024 11:21 PM, Thinh Nguyen wrote:
> Hi,
>
> On Fri, Sep 13, 2024, Selvarasu Ganesan wrote:
>> Hi Thinh,
>>
>> So far, there have been no reported error instances. But, we suspecting
>> that the issue may be related to our glue driver. In our glue driver, we
>> access the reference of evt->flags when starting or stopping the gadget
>> based on a VBUS notification. We apologize for sharing this information
>> so late, as we only became aware of it recently.
>>
>> The following sequence outlines the possible scenarios of race conditions:
>>
>> Thread#1 (Our glue Driver Sequence)
>> ===================================
>> ->USB VBUS notification
>> ->Start/Stop gadget
>> ->dwc->ev_buf->flags |= BIT(20); (It's for our reference)
>> ->Call dwc3 exynos runtime suspend/resume
>> ->dwc->ev_buf->flags &= ~BIT(20);
>> ->Call dwc3 core runtime suspend/resume
>>
>> Thread#2
>> ========
>> ->dwc3_interrupt()
>> ->evt->flags |= DWC3_EVENT_PENDING;
>> ->dwc3_thread_interrupt()
>> ->evt->flags &= ~DWC3_EVENT_PENDING;
>>
> This is great! That's likely the problem. Glad you found it.
>
>>
>> After our internal discussions, we have decided to remove the
>> unnecessary access to evt->flag in our glue driver. We have made these
>> changes and initiated testing.
>>
>> Thank you for your help so far to understand more into our glue driver code.
>>
>> And We are thinking that it would be fine to reset evt->flag when the
>> USB controller is started, along with the changes you suggested earlier.
>> This additional measure will help prevent similar issues from occurring
>> in the future.
>>
>> Please let us know your thoughts on this proposal. If it is not
>> necessary, we understand and will proceed accordingly.
>>
> You can submit the change I suggested. That's a valid change. However,
> we should not include the reset of the DWC3_EVENT_PENDING flag. Had we
> done this, you may not found the issue above. It serves no purpose for
> the core driver logic and will be an extra burden for us to maintain. (I
> don't want to scratch my head in the future to figure out why that
> change was needed or concern whether it can be removed without causing
> regression).

Yeah I understand.

Please reconfirm the below changes once with commit message. I will post 
new version if this changes are fine.


[PATCH] usb: dwc3: core: Stop processing of pending events if controller 
is halted

This commit addresses an issue where events were being processed when
the controller was in a halted state. To fix this issue by stop
processing the events as the event count was considered stale or
invalid when the controller was halted.

Fixes: fc8bb91bc83e ("usb: dwc3: implement runtime PM")
Cc: stable <stable@kernel.org>
Signed-off-by: Selvarasu Ganesan <selvarasu.g@samsung.com>
Suggested-by: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
---
  drivers/usb/dwc3/core.c   | 17 +++++++++++++++--
  drivers/usb/dwc3/core.h   |  4 ----
  drivers/usb/dwc3/gadget.c | 22 +++++++++++-----------
  3 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index 9eb085f359ce..f47b20bc2d1f 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -544,6 +544,7 @@ static int dwc3_alloc_event_buffers(struct dwc3 
*dwc, unsigned int length)
  int dwc3_event_buffers_setup(struct dwc3 *dwc)
  {
         struct dwc3_event_buffer        *evt;
+       u32                             reg;

         if (!dwc->ev_buf)
                 return 0;
@@ -556,8 +557,10 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
                         upper_32_bits(evt->dma));
         dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0),
                         DWC3_GEVNTSIZ_SIZE(evt->length));
-       dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), 0);

+       /* Clear any stale event */
+       reg = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
+       dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), reg);
         return 0;
  }

@@ -2499,7 +2502,11 @@ static int dwc3_runtime_resume(struct device *dev)

         switch (dwc->current_dr_role) {
         case DWC3_GCTL_PRTCAP_DEVICE:
-               dwc3_gadget_process_pending_events(dwc);
+               if (dwc->pending_events) {
+                       pm_runtime_put(dwc->dev);
+                       dwc->pending_events = false;
+                       enable_irq(dwc->irq_gadget);
+               }
                 break;
         case DWC3_GCTL_PRTCAP_HOST:
         default:
@@ -2589,6 +2596,12 @@ static void dwc3_complete(struct device *dev)
  static const struct dev_pm_ops dwc3_dev_pm_ops = {
         SET_SYSTEM_SLEEP_PM_OPS(dwc3_suspend, dwc3_resume)
         .complete = dwc3_complete,
+
+       /*
+        * Runtime suspend halts the controller on disconnection. It 
replies on
+        * platforms with custom connection notification to start the 
controller
+        * again.
+        */
         SET_RUNTIME_PM_OPS(dwc3_runtime_suspend, dwc3_runtime_resume,
                         dwc3_runtime_idle)
  };
diff --git a/drivers/usb/dwc3/core.h b/drivers/usb/dwc3/core.h
index c71240e8f7c7..9c508e0c5cdf 100644
--- a/drivers/usb/dwc3/core.h
+++ b/drivers/usb/dwc3/core.h
@@ -1675,7 +1675,6 @@ static inline void dwc3_otg_host_init(struct dwc3 
*dwc)
  #if !IS_ENABLED(CONFIG_USB_DWC3_HOST)
  int dwc3_gadget_suspend(struct dwc3 *dwc);
  int dwc3_gadget_resume(struct dwc3 *dwc);
-void dwc3_gadget_process_pending_events(struct dwc3 *dwc);
  #else
  static inline int dwc3_gadget_suspend(struct dwc3 *dwc)
  {
@@ -1687,9 +1686,6 @@ static inline int dwc3_gadget_resume(struct dwc3 *dwc)
         return 0;
  }

-static inline void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
-{
-}
  #endif /* !IS_ENABLED(CONFIG_USB_DWC3_HOST) */

  #if IS_ENABLED(CONFIG_USB_DWC3_ULPI)
diff --git a/drivers/usb/dwc3/gadget.c b/drivers/usb/dwc3/gadget.c
index 291bc549935b..a32c3a292353 100644
--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -4483,6 +4483,17 @@ static irqreturn_t dwc3_check_event_buf(struct 
dwc3_event_buffer *evt)
                 return IRQ_HANDLED;

         count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
+
+       /*
+        * If the controller is halted, the event count is 
stale/invalid. Ignore
+        * them. This happens if the interrupt assertion is from an 
out-of-band
+        * resume notification.
+        */
+       if (!dwc->pullups_connected && count) {
+               dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), count);
+               return IRQ_HANDLED;
+       }
+
         count &= DWC3_GEVNTCOUNT_MASK;
         if (!count)
                 return IRQ_NONE;
@@ -4728,14 +4739,3 @@ int dwc3_gadget_resume(struct dwc3 *dwc)

         return dwc3_gadget_soft_connect(dwc);
  }
-
-void dwc3_gadget_process_pending_events(struct dwc3 *dwc)
-{
-       if (dwc->pending_events) {
-               dwc3_interrupt(dwc->irq_gadget, dwc->ev_buf);
-               dwc3_thread_interrupt(dwc->irq_gadget, dwc->ev_buf);
-               pm_runtime_put(dwc->dev);
-               dwc->pending_events = false;
-               enable_irq(dwc->irq_gadget);
-       }
-}
--
2.17.1

Thanks,
Selva
> Thanks,
> Thinh