Hi,
Manu Gautam <mgautam@xxxxxxxxxxxxxx> writes:
> Hi,
>
> On 10/31/2017 4:12 PM, Felipe Balbi wrote:
>> 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 :-)
>
> If SSPHY is not present on this platform(?) or maximum_speed = HS then we can
> avoid overriding max-speed to SS?
The problem here is that we have a SS controller with a HS-only
PHY. However, dwc3 revision is old enough that it has this erratum about
metasbility state on Run/Stop bit if we try to change maximum operating
speed for the controller.
--
balbi
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