Hi,
Roger Quadros <rogerq@xxxxxx> writes:
> 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 :-)
>>
>
> The TI kernel releases have been ignoring this workaround for quite sometime now and
> there haven't been any surprises.
> I'd be happy to have a flag so I don't have to keep porting a patch around :).
>
> Should I add a DT property?
> "snps,dis_metastability_quirk"?
Sure, we can send that on the next merge window (v4.15). Just make sure
to REALLY make it clear that this is a dangerous flag and should only be
enabled if you really, really know what you're doing :-)
--
balbi
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