In certain scenarios, there is a chance that the CPU may not be
scheduled the bottom half of dwc3 interrupt. This is because the CPU
may hang up where any work queue lockup has happened for the same CPU
that is trying to schedule the dwc3 thread interrupt. In this scenario,
the USB can enter runtime suspend as the bus may idle for a longer time
, or user can reconnect the USB cable. Then, the dwc3 event interrupt
can be enabled when runtime resume is happening with regardless of the
previous event status. This can lead to a dwc3 IRQ storm due to the
return from the interrupt handler by checking only the evt->flags as
DWC3_EVENT_PENDING, where the same flag was set as DWC3_EVENT_PENDING
in previous work queue lockup.
Let's consider the following sequences in this scenario,
Call trace of dwc3 IRQ after workqueue lockup scenario
======================================================
IRQ #1:
->dwc3_interrupt()
->dwc3_check_event_buf()
->if (evt->flags & DWC3_EVENT_PENDING)
return IRQ_HANDLED;
->evt->flags |= DWC3_EVENT_PENDING;
->/* Disable interrupt by setting DWC3_GEVNTSIZ_INTMASK in
DWC3_GEVNTSIZ
->return IRQ_WAKE_THREAD; // No workqueue scheduled for dwc3
thread_fu due to workqueue lockup
even after return IRQ_WAKE_THREAD
from top-half.
Thread #2:
->dwc3_runtime_resume()
->dwc3_resume_common()
->dwc3_gadget_resume()
->dwc3_gadget_soft_connect()
->dwc3_event_buffers_setup()
->/*Enable interrupt by clearing DWC3_GEVNTSIZ_INTMASK in
DWC3_GEVNTSIZ*/
Start IRQ Storming after enable dwc3 event in resume path
=========================================================
CPU0: IRQ
dwc3_interrupt()
dwc3_check_event_buf()
if (evt->flags & DWC3_EVENT_PENDING)
return IRQ_HANDLED;
CPU0: IRQ
dwc3_interrupt()
dwc3_check_event_buf()
if (evt->flags & DWC3_EVENT_PENDING)
return IRQ_HANDLED;
..
..
To fix this issue by avoiding enabling of the dwc3 event interrupt in
the runtime resume path if dwc3 event processing is in progress.
Signed-off-by: Selvarasu Ganesan <selvarasu.g@xxxxxxxxxxx>
---
drivers/usb/dwc3/core.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
index cb82557678dd..610792a70805 100644
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -549,8 +549,12 @@ int dwc3_event_buffers_setup(struct dwc3 *dwc)
lower_32_bits(evt->dma));
dwc3_writel(dwc->regs, DWC3_GEVNTADRHI(0),
upper_32_bits(evt->dma));
- dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0),
- DWC3_GEVNTSIZ_SIZE(evt->length));
+
+ /* Skip enable dwc3 event interrupt if event is processing in middle */
+ if (!(evt->flags & DWC3_EVENT_PENDING))
+ dwc3_writel(dwc->regs, DWC3_GEVNTSIZ(0),
+ DWC3_GEVNTSIZ_SIZE(evt->length));
+
dwc3_writel(dwc->regs, DWC3_GEVNTCOUNT(0), 0);
return 0;
--
2.17.1
