On 9/7/2024 6:09 AM, Thinh Nguyen wrote:
> On Sat, Sep 07, 2024, Selvarasu Ganesan wrote:
>> Hi Thinh,
>>
>> I ran the code you recommended on our testing environment and was able
>> to reproduce the issue one time.
>>
>> When evt->flags contains DWC3_EVENT_PENDING, I've included the following
>> debugging information: I added this debug message at the start of
>> dwc3_event_buffers_cleanup and dwc3_event_buffers_setup functions in
>> during suspend and resume.
>>
>> The results were quite interesting . I'm curious to understand how
>> evt->flags is set to DWC3_EVENT_PENDING, and along with DWC3_GEVNTSIZ is
>> equal to 0x1000 during the suspend.
> That is indeed strange.
>
>> Its means that the previous bottom-half handler prior to suspend might
>> still be executing in the middle of the process.
>>
>> Could you please give your suggestions here? And let me know if anything
>> want to test or additional details are required.
>>
>>
>> ##DBG: dwc3_event_buffers_cleanup:
>> evt->length :0x1000
>> evt->lpos :0x20c
>> evt->count :0x0
>> evt->flags :0x1 // This is Unexpected if DWC3_GEVNTSIZ(0)(0xc408):
>> 0x00001000. Its means that previous bottom-half handler may be still
>> running in middle
> Perhaps.
>
> But I doubt that's the case since it shouldn't take that long for the
> bottom-half to be completed before the next resume yet the flag is still
> set.
>
>> DWC3_GEVNTSIZ(0)(0xc408) : 0x00001000
>> DWC3_GEVNTCOUNT(0)(0xc40c) : 0x00000000
>> DWC3_DCFG(0xc700) : 0x00e008a8
>> DWC3_DCTL(0xc704) : 0x0cf00a00
>> DWC3_DEVTEN(0xc708) : 0x00000000
>> DWC3_DSTS(0xc70c) : 0x00d20cd1
>>
> The controller status is halted. So there's no problem with
> soft-disconnect. For the interrupt mask in GEVNTSIZ to be cleared,
> that likely means that the bottom-half had probably completed.
Agree, But I am worrying on If the bottom-half is completed, then
DWC3_EVENT_PENDING must be cleared in evt->flags.
Is there any possibility of a CPU reordering issue when updating
evt->flags in the bottom-half handler?.
Should I try with wmb() when writing to evt->flags?
>
>> ##DBG: dwc3_event_buffers_setup:
>> evt->length :0x1000
>> evt->lpos :0x20c
> They fact that evt->lpos did not get updated tells me that there's
> something wrong with memory access to your platform during suspend and
> resume.
Are you expecting the evt->lpos value to be zero here? If so, this is
expected in our test setup because we avoid writing zero to evt->lpos as
part of dwc3_event_buffers_cleanup if evt->flags have a value of 1. This
is simply to track the status of evt->lpos during suspend to resume when
evt->flags have a value of DWC3_EVENT_PENDING. The following test codes
for the reference.
--- a/drivers/usb/dwc3/core.c
+++ b/drivers/usb/dwc3/core.c
@@ -505,8 +505,20 @@ 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;
evt = dwc->ev_buf;
+
+ if (evt->flags & DWC3_EVENT_PENDING) {
+ pr_info("evt->length :%x\n", evt->length);
+ pr_info("evt->lpos :%x\n", evt->lpos);
+ pr_info("evt->count :%x\n", evt->count);
+ pr_info("evt->flags :%x\n", evt->flags);
+
+ dwc3_exynos_reg_dump(dwc);
+
+ }
+
evt->lpos = 0;
dwc3_writel(dwc->regs, DWC3_GEVNTADRLO(0),
lower_32_bits(evt->dma));
@@ -514,8 +526,10 @@ 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;
}
@@ -525,7 +539,16 @@ void dwc3_event_buffers_cleanup(struct dwc3 *dwc)
evt = dwc->ev_buf;
- evt->lpos = 0;
+ if (evt->flags & DWC3_EVENT_PENDING) {
+ pr_info("evt->length :%x\n", evt->length);
+ pr_info("evt->lpos :%x\n", evt->lpos);
+ pr_info("evt->count :%x\n", evt->count);
+ pr_info("evt->flags :%x\n", evt->flags);
+
+ dwc3_exynos_reg_dump(dwc);
+ } else {
+ evt->lpos = 0;
+ }
>
>> evt->count :0x0
>> evt->flags :0x1 // Still It's not clearing in during resume.
>>
>> DWC3_GEVNTSIZ(0)(0xc408) : 0x00000000
>> DWC3_GEVNTCOUNT(0)(0xc40c) : 0x00000000
>> DWC3_DCFG(0xc700) : 0x00080800
>> DWC3_DCTL(0xc704) : 0x00f00000
>> DWC3_DEVTEN(0xc708) : 0x00000000
>> DWC3_DSTS(0xc70c) : 0x00d20001
>>
> Please help look into your platform to see what condition triggers this
> memory access issue. If this is a hardware quirk, we can properly update
> the change and note it to be so.
Sure I will try to figure it out. However, we are facing challenges in
reproducing the issue. There could be a delay in understanding the
conditions that trigger the memory issue if it is related to a memory issue.
>
> Thanks,
> Thinh
>
> (If possible, for future tests, please dump the dwc3 tracepoints. Many
> thanks for the tests.)
I tried to get dwc3 traces in the failure case, but so far no instances
have been reported. Our testing is still in progress with enable dwc3
traces.
I will keep posting once I get the dwc3 traces in the failure scenario.
Thanks,
Selva
