Re: DWC3 Gadget backtrace

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Felipe,

On 31/10/17 12:24, Felipe Balbi wrote:
> 
> Hi,
> 
> Roger Quadros <rogerq@xxxxxx> writes:
> 
> <snip>
> 
>>> Roger, your PHY is toast :-(
>>>
>>>      irq/90-dwc3-969   [000] d...    52.323145: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    52.560646: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    52.798144: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    53.035646: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    53.273143: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    53.510657: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    53.748142: dwc3_event: event (00000901): Erratic Error [U0]
>>>      irq/90-dwc3-969   [000] d...    53.985640: dwc3_event: event (00000901): Erratic Error [U0]
>>>
>>
>> This is known issue due to operating a HighSpeed PHY in SuperSpeed mode.
>>
>> from dwc3/gadget.c:2015
>>
>>         /*
>>          * WORKAROUND: DWC3 revision < 2.20a have an issue
>>          * which would cause metastability state on Run/Stop
>>          * bit if we try to force the IP to USB2-only mode.
>>          *
>>          * Because of that, we cannot configure the IP to any
>>          * speed other than the SuperSpeed
>>          *
>>          * Refers to:
>>          *
>>          * STAR#9000525659: Clock Domain Crossing on DCTL in
>>          * USB 2.0 Mode
>>          */
>>         if (dwc->revision < DWC3_REVISION_220A) {
>>                 reg |= DWC3_DCFG_SUPERSPEED;
>>         } else {
>>
>> If we undo this workaround, the Erratic Error messages should go away.
> 
> right, I remember now. It's your call, if you wanna add a flag to ignore
> this STAR ticket, just keep in mind you'd have to cope with possible
> metastability on the Run/Stop bit :-)
> 

Actually AM437x uses rev 2.4a and is not affected by this. There is a problem
with dwc3_gadget_set_speed(). I'll send a fix for it.

We'll still need the flag for TI's DRA7 platform's USB2 instance though.

-- 
cheers,
-roger

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
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