Re: [PATCH v3 3/4] usb: dwc3: Add device property sgl-trb-cache-size-quirk

[Tejas Joglekar <Tejas.Joglekar@synopsys.com>]

Hello,

On 7/21/2020 3:17 PM, Felipe Balbi wrote:
> Tejas Joglekar <Tejas.Joglekar@synopsys.com> writes:
> 
>> Hi Rob,
>>
>> On 7/6/2020 12:13 PM, Felipe Balbi wrote:
>>>
>>> Hi,
>>>
>>> Tejas Joglekar <Tejas.Joglekar@synopsys.com> writes:
>>>>> @@ -95,6 +95,10 @@ int dwc3_host_init(struct dwc3 *dwc)
>>>>>  	if (dwc->usb2_lpm_disable)
>>>>>  		props[prop_idx++] = PROPERTY_ENTRY_BOOL("usb2-lpm-disable");
>>>>>  
>>>>> +	if (dwc->sgl_trb_cache_size_quirk)
>>>>> +		props[prop_idx++] =
>>>>> +			PROPERTY_ENTRY_BOOL("sgl-trb-cache-size-quirk");
>>>>> +
>>>>>  	/**
>>>>>  	 * WORKAROUND: dwc3 revisions <=3.00a have a limitation
>>>>>  	 * where Port Disable command doesn't work.
>>>>>
>>>> Does this implementation looks good to you? Rob has some concerned over the DT entries,
>>>> you suggested using compatible string with this quirk addition.
>>>> Can you please brief about how you would like to have this quirk implemented?
>>>> I can send the updated patch. My patch series is pending for merge just because of the
>>>> DT and quirk issue. Can you please help?
>>>
>>> Yeah, you need to get into an agreement with Rob :-) I don't mind having
>>> extra DT flags for things which can't be detected in runtime, Rob
>>> disagrees.
>>>
>> The compatible string is not suitable option as it does not work with platform drivers
>> with PCI based system. Also Synopsys controllers IP version register is not visible to xhci
>> driver and hence we don't have separate compatible string for each Synopsys version on the
>> xhci driver side. 
>> Due to which I depend on DT flag addition for the quirk. Can we add these DT flags and quirk?
> 
> As I said, I'm well aware of the situation regarding usage of compatible
> strings and the fact that dwc3 must work on PCI and non-PCI systems (I
> wrote the thing as it is after all). The person blocking new quirk flags
> is Rob, not me. You need to convince Rob that this is the way to go.
> 
@Felipe: Sorry for confusion if any, previous mail was intended for Rob asking about his approval.

> Rob, ball's in your court. Sorry.> 
@Rob: As I and Felipe have mentioned before, it is very much necessary to have quirk flags
for the current changes as compatible string would not be a solution for PCI and non-PCI
systems. Can you please approve this change ? If you have any concern about naming or any
other thing, please let us know.

Thanks & Regards,
 Tejas Joglekar